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7e7af3496e
The manual gives "an example showing how to handle failure to open a
file correctly." The example function, open_sesame, uses the
newly-introduced strerror function and errno and
program_invocation_short_name variables. It fails to specify GNU
extensions, however, so attempts to use it in the following way:
int main (void) {open_sesame ("badname");}
fail during compilation with "error: ‘program_invocation_short_name’
undeclared", indicating the example is incomplete. The presence of
"#include"s suggest everything neccesary for the function to work should
be present. For completeness, the example is lacking the following line:
#define _GNU_SOURCE
as the declarations of program_invocation_*name in errno.h are wrapped
in an "#ifdef __USE_GNU" conditional.
The documentation of the variables is also expanded, adding that their
definition lies in errno.h and noting specifically they are GNU
extensions.
1710 lines
57 KiB
Plaintext
1710 lines
57 KiB
Plaintext
@node Error Reporting, Memory, Introduction, Top
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@chapter Error Reporting
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@c %MENU% How library functions report errors
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@cindex error reporting
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@cindex reporting errors
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@cindex error codes
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@cindex status codes
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Many functions in @theglibc{} detect and report error conditions,
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and sometimes your programs need to check for these error conditions.
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For example, when you open an input file, you should verify that the
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file was actually opened correctly, and print an error message or take
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other appropriate action if the call to the library function failed.
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This chapter describes how the error reporting facility works. Your
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program should include the header file @file{errno.h} to use this
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facility.
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@pindex errno.h
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@menu
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* Checking for Errors:: How errors are reported by library functions.
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* Error Codes:: Error code macros; all of these expand
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into integer constant values.
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* Error Messages:: Mapping error codes onto error messages.
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@end menu
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@node Checking for Errors, Error Codes, , Error Reporting
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@section Checking for Errors
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Most library functions return a special value to indicate that they have
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failed. The special value is typically @code{-1}, a null pointer, or a
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constant such as @code{EOF} that is defined for that purpose. But this
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return value tells you only that an error has occurred. To find out
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what kind of error it was, you need to look at the error code stored in the
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variable @code{errno}. This variable is declared in the header file
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@file{errno.h}.
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@pindex errno.h
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@comment errno.h
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@comment ISO
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@deftypevr {Variable} {volatile int} errno
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The variable @code{errno} contains the system error number. You can
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change the value of @code{errno}.
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Since @code{errno} is declared @code{volatile}, it might be changed
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asynchronously by a signal handler; see @ref{Defining Handlers}.
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However, a properly written signal handler saves and restores the value
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of @code{errno}, so you generally do not need to worry about this
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possibility except when writing signal handlers.
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The initial value of @code{errno} at program startup is zero. Many
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library functions are guaranteed to set it to certain nonzero values
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when they encounter certain kinds of errors. These error conditions are
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listed for each function. These functions do not change @code{errno}
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when they succeed; thus, the value of @code{errno} after a successful
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call is not necessarily zero, and you should not use @code{errno} to
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determine @emph{whether} a call failed. The proper way to do that is
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documented for each function. @emph{If} the call failed, you can
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examine @code{errno}.
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Many library functions can set @code{errno} to a nonzero value as a
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result of calling other library functions which might fail. You should
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assume that any library function might alter @code{errno} when the
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function returns an error.
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@strong{Portability Note:} @w{ISO C} specifies @code{errno} as a
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``modifiable lvalue'' rather than as a variable, permitting it to be
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implemented as a macro. For example, its expansion might involve a
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function call, like @w{@code{*__errno_location ()}}. In fact, that is
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what it is
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on @gnulinuxhurdsystems{}. @Theglibc{}, on each system, does
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whatever is right for the particular system.
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There are a few library functions, like @code{sqrt} and @code{atan},
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that return a perfectly legitimate value in case of an error, but also
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set @code{errno}. For these functions, if you want to check to see
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whether an error occurred, the recommended method is to set @code{errno}
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to zero before calling the function, and then check its value afterward.
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@end deftypevr
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@pindex errno.h
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All the error codes have symbolic names; they are macros defined in
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@file{errno.h}. The names start with @samp{E} and an upper-case
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letter or digit; you should consider names of this form to be
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reserved names. @xref{Reserved Names}.
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The error code values are all positive integers and are all distinct,
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with one exception: @code{EWOULDBLOCK} and @code{EAGAIN} are the same.
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Since the values are distinct, you can use them as labels in a
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@code{switch} statement; just don't use both @code{EWOULDBLOCK} and
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@code{EAGAIN}. Your program should not make any other assumptions about
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the specific values of these symbolic constants.
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The value of @code{errno} doesn't necessarily have to correspond to any
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of these macros, since some library functions might return other error
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codes of their own for other situations. The only values that are
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guaranteed to be meaningful for a particular library function are the
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ones that this manual lists for that function.
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Except on @gnuhurdsystems{}, almost any system call can return @code{EFAULT} if
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it is given an invalid pointer as an argument. Since this could only
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happen as a result of a bug in your program, and since it will not
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happen on @gnuhurdsystems{}, we have saved space by not mentioning
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@code{EFAULT} in the descriptions of individual functions.
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In some Unix systems, many system calls can also return @code{EFAULT} if
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given as an argument a pointer into the stack, and the kernel for some
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obscure reason fails in its attempt to extend the stack. If this ever
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happens, you should probably try using statically or dynamically
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allocated memory instead of stack memory on that system.
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@node Error Codes, Error Messages, Checking for Errors, Error Reporting
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@section Error Codes
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@pindex errno.h
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The error code macros are defined in the header file @file{errno.h}.
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All of them expand into integer constant values. Some of these error
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codes can't occur on @gnusystems{}, but they can occur using @theglibc{}
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on other systems.
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@comment errno.h
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@comment POSIX.1: Operation not permitted
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@deftypevr Macro int EPERM
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@comment errno 1 @c DO NOT REMOVE
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Operation not permitted; only the owner of the file (or other resource)
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or processes with special privileges can perform the operation.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No such file or directory
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@deftypevr Macro int ENOENT
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@comment errno 2 @c DO NOT REMOVE
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No such file or directory. This is a ``file doesn't exist'' error
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for ordinary files that are referenced in contexts where they are
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expected to already exist.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No such process
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@deftypevr Macro int ESRCH
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@comment errno 3 @c DO NOT REMOVE
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No process matches the specified process ID.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Interrupted system call
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@deftypevr Macro int EINTR
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@comment errno 4 @c DO NOT REMOVE
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Interrupted function call; an asynchronous signal occurred and prevented
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completion of the call. When this happens, you should try the call
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again.
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You can choose to have functions resume after a signal that is handled,
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rather than failing with @code{EINTR}; see @ref{Interrupted
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Primitives}.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Input/output error
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@deftypevr Macro int EIO
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@comment errno 5 @c DO NOT REMOVE
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Input/output error; usually used for physical read or write errors.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No such device or address
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@deftypevr Macro int ENXIO
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@comment errno 6 @c DO NOT REMOVE
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No such device or address. The system tried to use the device
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represented by a file you specified, and it couldn't find the device.
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This can mean that the device file was installed incorrectly, or that
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the physical device is missing or not correctly attached to the
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computer.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Argument list too long
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@deftypevr Macro int E2BIG
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@comment errno 7 @c DO NOT REMOVE
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Argument list too long; used when the arguments passed to a new program
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being executed with one of the @code{exec} functions (@pxref{Executing a
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File}) occupy too much memory space. This condition never arises on
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@gnuhurdsystems{}.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Exec format error
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@deftypevr Macro int ENOEXEC
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@comment errno 8 @c DO NOT REMOVE
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Invalid executable file format. This condition is detected by the
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@code{exec} functions; see @ref{Executing a File}.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Bad file descriptor
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@deftypevr Macro int EBADF
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@comment errno 9 @c DO NOT REMOVE
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Bad file descriptor; for example, I/O on a descriptor that has been
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closed or reading from a descriptor open only for writing (or vice
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versa).
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No child processes
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@deftypevr Macro int ECHILD
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@comment errno 10 @c DO NOT REMOVE
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There are no child processes. This error happens on operations that are
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supposed to manipulate child processes, when there aren't any processes
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to manipulate.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Resource deadlock avoided
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@deftypevr Macro int EDEADLK
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@comment errno 11 @c DO NOT REMOVE
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Deadlock avoided; allocating a system resource would have resulted in a
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deadlock situation. The system does not guarantee that it will notice
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all such situations. This error means you got lucky and the system
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noticed; it might just hang. @xref{File Locks}, for an example.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Cannot allocate memory
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@deftypevr Macro int ENOMEM
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@comment errno 12 @c DO NOT REMOVE
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No memory available. The system cannot allocate more virtual memory
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because its capacity is full.
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@end deftypevr
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|
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@comment errno.h
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@comment POSIX.1: Permission denied
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@deftypevr Macro int EACCES
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@comment errno 13 @c DO NOT REMOVE
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Permission denied; the file permissions do not allow the attempted operation.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Bad address
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@deftypevr Macro int EFAULT
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@comment errno 14 @c DO NOT REMOVE
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Bad address; an invalid pointer was detected.
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On @gnuhurdsystems{}, this error never happens; you get a signal instead.
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@end deftypevr
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@comment errno.h
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@comment BSD: Block device required
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@deftypevr Macro int ENOTBLK
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@comment errno 15 @c DO NOT REMOVE
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A file that isn't a block special file was given in a situation that
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requires one. For example, trying to mount an ordinary file as a file
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system in Unix gives this error.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Device or resource busy
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@deftypevr Macro int EBUSY
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@comment errno 16 @c DO NOT REMOVE
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Resource busy; a system resource that can't be shared is already in use.
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For example, if you try to delete a file that is the root of a currently
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mounted filesystem, you get this error.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: File exists
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@deftypevr Macro int EEXIST
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@comment errno 17 @c DO NOT REMOVE
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File exists; an existing file was specified in a context where it only
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makes sense to specify a new file.
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@end deftypevr
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|
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@comment errno.h
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@comment POSIX.1: Invalid cross-device link
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@deftypevr Macro int EXDEV
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@comment errno 18 @c DO NOT REMOVE
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An attempt to make an improper link across file systems was detected.
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This happens not only when you use @code{link} (@pxref{Hard Links}) but
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also when you rename a file with @code{rename} (@pxref{Renaming Files}).
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No such device
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@deftypevr Macro int ENODEV
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@comment errno 19 @c DO NOT REMOVE
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The wrong type of device was given to a function that expects a
|
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particular sort of device.
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@end deftypevr
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|
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@comment errno.h
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@comment POSIX.1: Not a directory
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@deftypevr Macro int ENOTDIR
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@comment errno 20 @c DO NOT REMOVE
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A file that isn't a directory was specified when a directory is required.
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@end deftypevr
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|
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@comment errno.h
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@comment POSIX.1: Is a directory
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@deftypevr Macro int EISDIR
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@comment errno 21 @c DO NOT REMOVE
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File is a directory; you cannot open a directory for writing,
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or create or remove hard links to it.
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@end deftypevr
|
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|
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@comment errno.h
|
|
@comment POSIX.1: Invalid argument
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@deftypevr Macro int EINVAL
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@comment errno 22 @c DO NOT REMOVE
|
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Invalid argument. This is used to indicate various kinds of problems
|
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with passing the wrong argument to a library function.
|
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@end deftypevr
|
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|
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@comment errno.h
|
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@comment POSIX.1: Too many open files
|
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@deftypevr Macro int EMFILE
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@comment errno 24 @c DO NOT REMOVE
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The current process has too many files open and can't open any more.
|
|
Duplicate descriptors do count toward this limit.
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In BSD and GNU, the number of open files is controlled by a resource
|
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limit that can usually be increased. If you get this error, you might
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want to increase the @code{RLIMIT_NOFILE} limit or make it unlimited;
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@pxref{Limits on Resources}.
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@end deftypevr
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|
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@comment errno.h
|
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@comment POSIX.1: Too many open files in system
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@deftypevr Macro int ENFILE
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@comment errno 23 @c DO NOT REMOVE
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There are too many distinct file openings in the entire system. Note
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that any number of linked channels count as just one file opening; see
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@ref{Linked Channels}. This error never occurs on @gnuhurdsystems{}.
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@end deftypevr
|
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|
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@comment errno.h
|
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@comment POSIX.1: Inappropriate ioctl for device
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@deftypevr Macro int ENOTTY
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@comment errno 25 @c DO NOT REMOVE
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Inappropriate I/O control operation, such as trying to set terminal
|
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modes on an ordinary file.
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@end deftypevr
|
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|
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@comment errno.h
|
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@comment BSD: Text file busy
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@deftypevr Macro int ETXTBSY
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@comment errno 26 @c DO NOT REMOVE
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An attempt to execute a file that is currently open for writing, or
|
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write to a file that is currently being executed. Often using a
|
|
debugger to run a program is considered having it open for writing and
|
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will cause this error. (The name stands for ``text file busy''.) This
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is not an error on @gnuhurdsystems{}; the text is copied as necessary.
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@end deftypevr
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|
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@comment errno.h
|
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@comment POSIX.1: File too large
|
|
@deftypevr Macro int EFBIG
|
|
@comment errno 27 @c DO NOT REMOVE
|
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File too big; the size of a file would be larger than allowed by the system.
|
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@end deftypevr
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|
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@comment errno.h
|
|
@comment POSIX.1: No space left on device
|
|
@deftypevr Macro int ENOSPC
|
|
@comment errno 28 @c DO NOT REMOVE
|
|
No space left on device; write operation on a file failed because the
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disk is full.
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@end deftypevr
|
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|
|
@comment errno.h
|
|
@comment POSIX.1: Illegal seek
|
|
@deftypevr Macro int ESPIPE
|
|
@comment errno 29 @c DO NOT REMOVE
|
|
Invalid seek operation (such as on a pipe).
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Read-only file system
|
|
@deftypevr Macro int EROFS
|
|
@comment errno 30 @c DO NOT REMOVE
|
|
An attempt was made to modify something on a read-only file system.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Too many links
|
|
@deftypevr Macro int EMLINK
|
|
@comment errno 31 @c DO NOT REMOVE
|
|
Too many links; the link count of a single file would become too large.
|
|
@code{rename} can cause this error if the file being renamed already has
|
|
as many links as it can take (@pxref{Renaming Files}).
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Broken pipe
|
|
@deftypevr Macro int EPIPE
|
|
@comment errno 32 @c DO NOT REMOVE
|
|
Broken pipe; there is no process reading from the other end of a pipe.
|
|
Every library function that returns this error code also generates a
|
|
@code{SIGPIPE} signal; this signal terminates the program if not handled
|
|
or blocked. Thus, your program will never actually see @code{EPIPE}
|
|
unless it has handled or blocked @code{SIGPIPE}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment ISO: Numerical argument out of domain
|
|
@deftypevr Macro int EDOM
|
|
@comment errno 33 @c DO NOT REMOVE
|
|
Domain error; used by mathematical functions when an argument value does
|
|
not fall into the domain over which the function is defined.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment ISO: Numerical result out of range
|
|
@deftypevr Macro int ERANGE
|
|
@comment errno 34 @c DO NOT REMOVE
|
|
Range error; used by mathematical functions when the result value is
|
|
not representable because of overflow or underflow.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Resource temporarily unavailable
|
|
@deftypevr Macro int EAGAIN
|
|
@comment errno 35 @c DO NOT REMOVE
|
|
Resource temporarily unavailable; the call might work if you try again
|
|
later. The macro @code{EWOULDBLOCK} is another name for @code{EAGAIN};
|
|
they are always the same in @theglibc{}.
|
|
|
|
This error can happen in a few different situations:
|
|
|
|
@itemize @bullet
|
|
@item
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|
An operation that would block was attempted on an object that has
|
|
non-blocking mode selected. Trying the same operation again will block
|
|
until some external condition makes it possible to read, write, or
|
|
connect (whatever the operation). You can use @code{select} to find out
|
|
when the operation will be possible; @pxref{Waiting for I/O}.
|
|
|
|
@strong{Portability Note:} In many older Unix systems, this condition
|
|
was indicated by @code{EWOULDBLOCK}, which was a distinct error code
|
|
different from @code{EAGAIN}. To make your program portable, you should
|
|
check for both codes and treat them the same.
|
|
|
|
@item
|
|
A temporary resource shortage made an operation impossible. @code{fork}
|
|
can return this error. It indicates that the shortage is expected to
|
|
pass, so your program can try the call again later and it may succeed.
|
|
It is probably a good idea to delay for a few seconds before trying it
|
|
again, to allow time for other processes to release scarce resources.
|
|
Such shortages are usually fairly serious and affect the whole system,
|
|
so usually an interactive program should report the error to the user
|
|
and return to its command loop.
|
|
@end itemize
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Operation would block
|
|
@deftypevr Macro int EWOULDBLOCK
|
|
@comment errno EAGAIN @c DO NOT REMOVE
|
|
In @theglibc{}, this is another name for @code{EAGAIN} (above).
|
|
The values are always the same, on every operating system.
|
|
|
|
C libraries in many older Unix systems have @code{EWOULDBLOCK} as a
|
|
separate error code.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Operation now in progress
|
|
@deftypevr Macro int EINPROGRESS
|
|
@comment errno 36 @c DO NOT REMOVE
|
|
An operation that cannot complete immediately was initiated on an object
|
|
that has non-blocking mode selected. Some functions that must always
|
|
block (such as @code{connect}; @pxref{Connecting}) never return
|
|
@code{EAGAIN}. Instead, they return @code{EINPROGRESS} to indicate that
|
|
the operation has begun and will take some time. Attempts to manipulate
|
|
the object before the call completes return @code{EALREADY}. You can
|
|
use the @code{select} function to find out when the pending operation
|
|
has completed; @pxref{Waiting for I/O}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Operation already in progress
|
|
@deftypevr Macro int EALREADY
|
|
@comment errno 37 @c DO NOT REMOVE
|
|
An operation is already in progress on an object that has non-blocking
|
|
mode selected.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Socket operation on non-socket
|
|
@deftypevr Macro int ENOTSOCK
|
|
@comment errno 38 @c DO NOT REMOVE
|
|
A file that isn't a socket was specified when a socket is required.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Message too long
|
|
@deftypevr Macro int EMSGSIZE
|
|
@comment errno 40 @c DO NOT REMOVE
|
|
The size of a message sent on a socket was larger than the supported
|
|
maximum size.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Protocol wrong type for socket
|
|
@deftypevr Macro int EPROTOTYPE
|
|
@comment errno 41 @c DO NOT REMOVE
|
|
The socket type does not support the requested communications protocol.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Protocol not available
|
|
@deftypevr Macro int ENOPROTOOPT
|
|
@comment errno 42 @c DO NOT REMOVE
|
|
You specified a socket option that doesn't make sense for the
|
|
particular protocol being used by the socket. @xref{Socket Options}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Protocol not supported
|
|
@deftypevr Macro int EPROTONOSUPPORT
|
|
@comment errno 43 @c DO NOT REMOVE
|
|
The socket domain does not support the requested communications protocol
|
|
(perhaps because the requested protocol is completely invalid).
|
|
@xref{Creating a Socket}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Socket type not supported
|
|
@deftypevr Macro int ESOCKTNOSUPPORT
|
|
@comment errno 44 @c DO NOT REMOVE
|
|
The socket type is not supported.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Operation not supported
|
|
@deftypevr Macro int EOPNOTSUPP
|
|
@comment errno 45 @c DO NOT REMOVE
|
|
The operation you requested is not supported. Some socket functions
|
|
don't make sense for all types of sockets, and others may not be
|
|
implemented for all communications protocols. On @gnuhurdsystems{}, this
|
|
error can happen for many calls when the object does not support the
|
|
particular operation; it is a generic indication that the server knows
|
|
nothing to do for that call.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Protocol family not supported
|
|
@deftypevr Macro int EPFNOSUPPORT
|
|
@comment errno 46 @c DO NOT REMOVE
|
|
The socket communications protocol family you requested is not supported.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Address family not supported by protocol
|
|
@deftypevr Macro int EAFNOSUPPORT
|
|
@comment errno 47 @c DO NOT REMOVE
|
|
The address family specified for a socket is not supported; it is
|
|
inconsistent with the protocol being used on the socket. @xref{Sockets}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Address already in use
|
|
@deftypevr Macro int EADDRINUSE
|
|
@comment errno 48 @c DO NOT REMOVE
|
|
The requested socket address is already in use. @xref{Socket Addresses}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Cannot assign requested address
|
|
@deftypevr Macro int EADDRNOTAVAIL
|
|
@comment errno 49 @c DO NOT REMOVE
|
|
The requested socket address is not available; for example, you tried
|
|
to give a socket a name that doesn't match the local host name.
|
|
@xref{Socket Addresses}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Network is down
|
|
@deftypevr Macro int ENETDOWN
|
|
@comment errno 50 @c DO NOT REMOVE
|
|
A socket operation failed because the network was down.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Network is unreachable
|
|
@deftypevr Macro int ENETUNREACH
|
|
@comment errno 51 @c DO NOT REMOVE
|
|
A socket operation failed because the subnet containing the remote host
|
|
was unreachable.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Network dropped connection on reset
|
|
@deftypevr Macro int ENETRESET
|
|
@comment errno 52 @c DO NOT REMOVE
|
|
A network connection was reset because the remote host crashed.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Software caused connection abort
|
|
@deftypevr Macro int ECONNABORTED
|
|
@comment errno 53 @c DO NOT REMOVE
|
|
A network connection was aborted locally.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Connection reset by peer
|
|
@deftypevr Macro int ECONNRESET
|
|
@comment errno 54 @c DO NOT REMOVE
|
|
A network connection was closed for reasons outside the control of the
|
|
local host, such as by the remote machine rebooting or an unrecoverable
|
|
protocol violation.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: No buffer space available
|
|
@deftypevr Macro int ENOBUFS
|
|
@comment errno 55 @c DO NOT REMOVE
|
|
The kernel's buffers for I/O operations are all in use. In GNU, this
|
|
error is always synonymous with @code{ENOMEM}; you may get one or the
|
|
other from network operations.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Transport endpoint is already connected
|
|
@deftypevr Macro int EISCONN
|
|
@comment errno 56 @c DO NOT REMOVE
|
|
You tried to connect a socket that is already connected.
|
|
@xref{Connecting}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Transport endpoint is not connected
|
|
@deftypevr Macro int ENOTCONN
|
|
@comment errno 57 @c DO NOT REMOVE
|
|
The socket is not connected to anything. You get this error when you
|
|
try to transmit data over a socket, without first specifying a
|
|
destination for the data. For a connectionless socket (for datagram
|
|
protocols, such as UDP), you get @code{EDESTADDRREQ} instead.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Destination address required
|
|
@deftypevr Macro int EDESTADDRREQ
|
|
@comment errno 39 @c DO NOT REMOVE
|
|
No default destination address was set for the socket. You get this
|
|
error when you try to transmit data over a connectionless socket,
|
|
without first specifying a destination for the data with @code{connect}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Cannot send after transport endpoint shutdown
|
|
@deftypevr Macro int ESHUTDOWN
|
|
@comment errno 58 @c DO NOT REMOVE
|
|
The socket has already been shut down.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Too many references: cannot splice
|
|
@deftypevr Macro int ETOOMANYREFS
|
|
@comment errno 59 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Connection timed out
|
|
@deftypevr Macro int ETIMEDOUT
|
|
@comment errno 60 @c DO NOT REMOVE
|
|
A socket operation with a specified timeout received no response during
|
|
the timeout period.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Connection refused
|
|
@deftypevr Macro int ECONNREFUSED
|
|
@comment errno 61 @c DO NOT REMOVE
|
|
A remote host refused to allow the network connection (typically because
|
|
it is not running the requested service).
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Too many levels of symbolic links
|
|
@deftypevr Macro int ELOOP
|
|
@comment errno 62 @c DO NOT REMOVE
|
|
Too many levels of symbolic links were encountered in looking up a file name.
|
|
This often indicates a cycle of symbolic links.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: File name too long
|
|
@deftypevr Macro int ENAMETOOLONG
|
|
@comment errno 63 @c DO NOT REMOVE
|
|
Filename too long (longer than @code{PATH_MAX}; @pxref{Limits for
|
|
Files}) or host name too long (in @code{gethostname} or
|
|
@code{sethostname}; @pxref{Host Identification}).
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Host is down
|
|
@deftypevr Macro int EHOSTDOWN
|
|
@comment errno 64 @c DO NOT REMOVE
|
|
The remote host for a requested network connection is down.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: No route to host
|
|
@deftypevr Macro int EHOSTUNREACH
|
|
@comment errno 65 @c DO NOT REMOVE
|
|
The remote host for a requested network connection is not reachable.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Directory not empty
|
|
@deftypevr Macro int ENOTEMPTY
|
|
@comment errno 66 @c DO NOT REMOVE
|
|
Directory not empty, where an empty directory was expected. Typically,
|
|
this error occurs when you are trying to delete a directory.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Too many processes
|
|
@deftypevr Macro int EPROCLIM
|
|
@comment errno 67 @c DO NOT REMOVE
|
|
This means that the per-user limit on new process would be exceeded by
|
|
an attempted @code{fork}. @xref{Limits on Resources}, for details on
|
|
the @code{RLIMIT_NPROC} limit.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Too many users
|
|
@deftypevr Macro int EUSERS
|
|
@comment errno 68 @c DO NOT REMOVE
|
|
The file quota system is confused because there are too many users.
|
|
@c This can probably happen in a GNU system when using NFS.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Disk quota exceeded
|
|
@deftypevr Macro int EDQUOT
|
|
@comment errno 69 @c DO NOT REMOVE
|
|
The user's disk quota was exceeded.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Stale file handle
|
|
@deftypevr Macro int ESTALE
|
|
@comment errno 70 @c DO NOT REMOVE
|
|
Stale file handle. This indicates an internal confusion in the
|
|
file system which is due to file system rearrangements on the server host
|
|
for NFS file systems or corruption in other file systems.
|
|
Repairing this condition usually requires unmounting, possibly repairing
|
|
and remounting the file system.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Object is remote
|
|
@deftypevr Macro int EREMOTE
|
|
@comment errno 71 @c DO NOT REMOVE
|
|
An attempt was made to NFS-mount a remote file system with a file name that
|
|
already specifies an NFS-mounted file.
|
|
(This is an error on some operating systems, but we expect it to work
|
|
properly on @gnuhurdsystems{}, making this error code impossible.)
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC struct is bad
|
|
@deftypevr Macro int EBADRPC
|
|
@comment errno 72 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC version wrong
|
|
@deftypevr Macro int ERPCMISMATCH
|
|
@comment errno 73 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC program not available
|
|
@deftypevr Macro int EPROGUNAVAIL
|
|
@comment errno 74 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC program version wrong
|
|
@deftypevr Macro int EPROGMISMATCH
|
|
@comment errno 75 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC bad procedure for program
|
|
@deftypevr Macro int EPROCUNAVAIL
|
|
@comment errno 76 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: No locks available
|
|
@deftypevr Macro int ENOLCK
|
|
@comment errno 77 @c DO NOT REMOVE
|
|
No locks available. This is used by the file locking facilities; see
|
|
@ref{File Locks}. This error is never generated by @gnuhurdsystems{}, but
|
|
it can result from an operation to an NFS server running another
|
|
operating system.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Inappropriate file type or format
|
|
@deftypevr Macro int EFTYPE
|
|
@comment errno 79 @c DO NOT REMOVE
|
|
Inappropriate file type or format. The file was the wrong type for the
|
|
operation, or a data file had the wrong format.
|
|
|
|
On some systems @code{chmod} returns this error if you try to set the
|
|
sticky bit on a non-directory file; @pxref{Setting Permissions}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Authentication error
|
|
@deftypevr Macro int EAUTH
|
|
@comment errno 80 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Need authenticator
|
|
@deftypevr Macro int ENEEDAUTH
|
|
@comment errno 81 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Function not implemented
|
|
@deftypevr Macro int ENOSYS
|
|
@comment errno 78 @c DO NOT REMOVE
|
|
Function not implemented. This indicates that the function called is
|
|
not implemented at all, either in the C library itself or in the
|
|
operating system. When you get this error, you can be sure that this
|
|
particular function will always fail with @code{ENOSYS} unless you
|
|
install a new version of the C library or the operating system.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Not supported
|
|
@deftypevr Macro int ENOTSUP
|
|
@comment errno 118 @c DO NOT REMOVE
|
|
Not supported. A function returns this error when certain parameter
|
|
values are valid, but the functionality they request is not available.
|
|
This can mean that the function does not implement a particular command
|
|
or option value or flag bit at all. For functions that operate on some
|
|
object given in a parameter, such as a file descriptor or a port, it
|
|
might instead mean that only @emph{that specific object} (file
|
|
descriptor, port, etc.) is unable to support the other parameters given;
|
|
different file descriptors might support different ranges of parameter
|
|
values.
|
|
|
|
If the entire function is not available at all in the implementation,
|
|
it returns @code{ENOSYS} instead.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment ISO: Invalid or incomplete multibyte or wide character
|
|
@deftypevr Macro int EILSEQ
|
|
@comment errno 106 @c DO NOT REMOVE
|
|
While decoding a multibyte character the function came along an invalid
|
|
or an incomplete sequence of bytes or the given wide character is invalid.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: Inappropriate operation for background process
|
|
@deftypevr Macro int EBACKGROUND
|
|
@comment errno 100 @c DO NOT REMOVE
|
|
On @gnuhurdsystems{}, servers supporting the @code{term} protocol return
|
|
this error for certain operations when the caller is not in the
|
|
foreground process group of the terminal. Users do not usually see this
|
|
error because functions such as @code{read} and @code{write} translate
|
|
it into a @code{SIGTTIN} or @code{SIGTTOU} signal. @xref{Job Control},
|
|
for information on process groups and these signals.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: Translator died
|
|
@deftypevr Macro int EDIED
|
|
@comment errno 101 @c DO NOT REMOVE
|
|
On @gnuhurdsystems{}, opening a file returns this error when the file is
|
|
translated by a program and the translator program dies while starting
|
|
up, before it has connected to the file.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: ?
|
|
@deftypevr Macro int ED
|
|
@comment errno 102 @c DO NOT REMOVE
|
|
The experienced user will know what is wrong.
|
|
@c This error code is a joke. Its perror text is part of the joke.
|
|
@c Don't change it.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: You really blew it this time
|
|
@deftypevr Macro int EGREGIOUS
|
|
@comment errno 103 @c DO NOT REMOVE
|
|
You did @strong{what}?
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: Computer bought the farm
|
|
@deftypevr Macro int EIEIO
|
|
@comment errno 104 @c DO NOT REMOVE
|
|
Go home and have a glass of warm, dairy-fresh milk.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: Gratuitous error
|
|
@deftypevr Macro int EGRATUITOUS
|
|
@comment errno 105 @c DO NOT REMOVE
|
|
This error code has no purpose.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Bad message
|
|
@deftypevr Macro int EBADMSG
|
|
@comment errno 107
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Identifier removed
|
|
@deftypevr Macro int EIDRM
|
|
@comment errno 108
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Multihop attempted
|
|
@deftypevr Macro int EMULTIHOP
|
|
@comment errno 109
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: No data available
|
|
@deftypevr Macro int ENODATA
|
|
@comment errno 110
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Link has been severed
|
|
@deftypevr Macro int ENOLINK
|
|
@comment errno 111
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: No message of desired type
|
|
@deftypevr Macro int ENOMSG
|
|
@comment errno 112
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Out of streams resources
|
|
@deftypevr Macro int ENOSR
|
|
@comment errno 113
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Device not a stream
|
|
@deftypevr Macro int ENOSTR
|
|
@comment errno 114
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Value too large for defined data type
|
|
@deftypevr Macro int EOVERFLOW
|
|
@comment errno 115
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Protocol error
|
|
@deftypevr Macro int EPROTO
|
|
@comment errno 116
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Timer expired
|
|
@deftypevr Macro int ETIME
|
|
@comment errno 117
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Operation canceled
|
|
@deftypevr Macro int ECANCELED
|
|
@comment errno 119
|
|
Operation canceled; an asynchronous operation was canceled before it
|
|
completed. @xref{Asynchronous I/O}. When you call @code{aio_cancel},
|
|
the normal result is for the operations affected to complete with this
|
|
error; @pxref{Cancel AIO Operations}.
|
|
@end deftypevr
|
|
|
|
|
|
@emph{The following error codes are defined by the Linux/i386 kernel.
|
|
They are not yet documented.}
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Interrupted system call should be restarted
|
|
@deftypevr Macro int ERESTART
|
|
@comment errno ???/85
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Channel number out of range
|
|
@deftypevr Macro int ECHRNG
|
|
@comment errno ???/44
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Obsolete: Level 2 not synchronized
|
|
@deftypevr Macro int EL2NSYNC
|
|
@comment errno ???/45
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Obsolete: Level 3 halted
|
|
@deftypevr Macro int EL3HLT
|
|
@comment errno ???/46
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Obsolete: Level 3 reset
|
|
@deftypevr Macro int EL3RST
|
|
@comment errno ???/47
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Link number out of range
|
|
@deftypevr Macro int ELNRNG
|
|
@comment errno ???/48
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Protocol driver not attached
|
|
@deftypevr Macro int EUNATCH
|
|
@comment errno ???/49
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: No CSI structure available
|
|
@deftypevr Macro int ENOCSI
|
|
@comment errno ???/50
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Obsolete: Level 2 halted
|
|
@deftypevr Macro int EL2HLT
|
|
@comment errno ???/51
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Invalid exchange
|
|
@deftypevr Macro int EBADE
|
|
@comment errno ???/52
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Invalid request descriptor
|
|
@deftypevr Macro int EBADR
|
|
@comment errno ???/53
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Exchange full
|
|
@deftypevr Macro int EXFULL
|
|
@comment errno ???/54
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: No anode
|
|
@deftypevr Macro int ENOANO
|
|
@comment errno ???/55
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Invalid request code
|
|
@deftypevr Macro int EBADRQC
|
|
@comment errno ???/56
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Invalid slot
|
|
@deftypevr Macro int EBADSLT
|
|
@comment errno ???/57
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: File locking deadlock error
|
|
@deftypevr Macro int EDEADLOCK
|
|
@comment errno ???/58
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Bad font file format
|
|
@deftypevr Macro int EBFONT
|
|
@comment errno ???/59
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Machine is not on the network
|
|
@deftypevr Macro int ENONET
|
|
@comment errno ???/64
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Package not installed
|
|
@deftypevr Macro int ENOPKG
|
|
@comment errno ???/65
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Advertise error
|
|
@deftypevr Macro int EADV
|
|
@comment errno ???/68
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Srmount error
|
|
@deftypevr Macro int ESRMNT
|
|
@comment errno ???/69
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Communication error on send
|
|
@deftypevr Macro int ECOMM
|
|
@comment errno ???/70
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: RFS specific error
|
|
@deftypevr Macro int EDOTDOT
|
|
@comment errno ???/73
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Name not unique on network
|
|
@deftypevr Macro int ENOTUNIQ
|
|
@comment errno ???/76
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: File descriptor in bad state
|
|
@deftypevr Macro int EBADFD
|
|
@comment errno ???/77
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Remote address changed
|
|
@deftypevr Macro int EREMCHG
|
|
@comment errno ???/78
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Can not access a needed shared library
|
|
@deftypevr Macro int ELIBACC
|
|
@comment errno ???/79
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Accessing a corrupted shared library
|
|
@deftypevr Macro int ELIBBAD
|
|
@comment errno ???/80
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: .lib section in a.out corrupted
|
|
@deftypevr Macro int ELIBSCN
|
|
@comment errno ???/81
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Attempting to link in too many shared libraries
|
|
@deftypevr Macro int ELIBMAX
|
|
@comment errno ???/82
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Cannot exec a shared library directly
|
|
@deftypevr Macro int ELIBEXEC
|
|
@comment errno ???/83
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Streams pipe error
|
|
@deftypevr Macro int ESTRPIPE
|
|
@comment errno ???/86
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Structure needs cleaning
|
|
@deftypevr Macro int EUCLEAN
|
|
@comment errno ???/117
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Not a XENIX named type file
|
|
@deftypevr Macro int ENOTNAM
|
|
@comment errno ???/118
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: No XENIX semaphores available
|
|
@deftypevr Macro int ENAVAIL
|
|
@comment errno ???/119
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Is a named type file
|
|
@deftypevr Macro int EISNAM
|
|
@comment errno ???/120
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Remote I/O error
|
|
@deftypevr Macro int EREMOTEIO
|
|
@comment errno ???/121
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: No medium found
|
|
@deftypevr Macro int ENOMEDIUM
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Wrong medium type
|
|
@deftypevr Macro int EMEDIUMTYPE
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Required key not available
|
|
@deftypevr Macro int ENOKEY
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Key has expired
|
|
@deftypevr Macro int EKEYEXPIRED
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Key has been revoked
|
|
@deftypevr Macro int EKEYREVOKED
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Key was rejected by service
|
|
@deftypevr Macro int EKEYREJECTED
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Owner died
|
|
@deftypevr Macro int EOWNERDEAD
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: State not recoverable
|
|
@deftypevr Macro int ENOTRECOVERABLE
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Operation not possible due to RF-kill
|
|
@deftypevr Macro int ERFKILL
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Memory page has hardware error
|
|
@deftypevr Macro int EHWPOISON
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@node Error Messages, , Error Codes, Error Reporting
|
|
@section Error Messages
|
|
|
|
The library has functions and variables designed to make it easy for
|
|
your program to report informative error messages in the customary
|
|
format about the failure of a library call. The functions
|
|
@code{strerror} and @code{perror} give you the standard error message
|
|
for a given error code; the variable
|
|
@w{@code{program_invocation_short_name}} gives you convenient access to the
|
|
name of the program that encountered the error.
|
|
|
|
@comment string.h
|
|
@comment ISO
|
|
@deftypefun {char *} strerror (int @var{errnum})
|
|
@safety{@prelim{}@mtunsafe{@mtasurace{:strerror}}@asunsafe{@ascuheap{} @ascuintl{}}@acunsafe{@acsmem{}}}
|
|
@c Calls strerror_r with a static buffer allocated with malloc on the
|
|
@c first use.
|
|
The @code{strerror} function maps the error code (@pxref{Checking for
|
|
Errors}) specified by the @var{errnum} argument to a descriptive error
|
|
message string. The return value is a pointer to this string.
|
|
|
|
The value @var{errnum} normally comes from the variable @code{errno}.
|
|
|
|
You should not modify the string returned by @code{strerror}. Also, if
|
|
you make subsequent calls to @code{strerror}, the string might be
|
|
overwritten. (But it's guaranteed that no library function ever calls
|
|
@code{strerror} behind your back.)
|
|
|
|
The function @code{strerror} is declared in @file{string.h}.
|
|
@end deftypefun
|
|
|
|
@comment string.h
|
|
@comment GNU
|
|
@deftypefun {char *} strerror_r (int @var{errnum}, char *@var{buf}, size_t @var{n})
|
|
@safety{@prelim{}@mtsafe{}@asunsafe{@ascuintl{}}@acunsafe{}}
|
|
The @code{strerror_r} function works like @code{strerror} but instead of
|
|
returning the error message in a statically allocated buffer shared by
|
|
all threads in the process, it returns a private copy for the
|
|
thread. This might be either some permanent global data or a message
|
|
string in the user supplied buffer starting at @var{buf} with the
|
|
length of @var{n} bytes.
|
|
|
|
At most @var{n} characters are written (including the NUL byte) so it is
|
|
up to the user to select the buffer large enough.
|
|
|
|
This function should always be used in multi-threaded programs since
|
|
there is no way to guarantee the string returned by @code{strerror}
|
|
really belongs to the last call of the current thread.
|
|
|
|
This function @code{strerror_r} is a GNU extension and it is declared in
|
|
@file{string.h}.
|
|
@end deftypefun
|
|
|
|
@comment stdio.h
|
|
@comment ISO
|
|
@deftypefun void perror (const char *@var{message})
|
|
@safety{@prelim{}@mtsafe{@mtasurace{:stderr}}@asunsafe{@asucorrupt{} @ascuintl{} @ascuheap{} @asulock{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{} @acsfd{}}}
|
|
@c Besides strerror_r's and some of fprintf's issues, if stderr is not
|
|
@c oriented yet, create a new stream with a dup of stderr's fd and write
|
|
@c to that instead of stderr, to avoid orienting it.
|
|
This function prints an error message to the stream @code{stderr};
|
|
see @ref{Standard Streams}. The orientation of @code{stderr} is not
|
|
changed.
|
|
|
|
If you call @code{perror} with a @var{message} that is either a null
|
|
pointer or an empty string, @code{perror} just prints the error message
|
|
corresponding to @code{errno}, adding a trailing newline.
|
|
|
|
If you supply a non-null @var{message} argument, then @code{perror}
|
|
prefixes its output with this string. It adds a colon and a space
|
|
character to separate the @var{message} from the error string corresponding
|
|
to @code{errno}.
|
|
|
|
The function @code{perror} is declared in @file{stdio.h}.
|
|
@end deftypefun
|
|
|
|
@code{strerror} and @code{perror} produce the exact same message for any
|
|
given error code; the precise text varies from system to system. With
|
|
@theglibc{}, the messages are fairly short; there are no multi-line
|
|
messages or embedded newlines. Each error message begins with a capital
|
|
letter and does not include any terminating punctuation.
|
|
|
|
@cindex program name
|
|
@cindex name of running program
|
|
Many programs that don't read input from the terminal are designed to
|
|
exit if any system call fails. By convention, the error message from
|
|
such a program should start with the program's name, sans directories.
|
|
You can find that name in the variable
|
|
@code{program_invocation_short_name}; the full file name is stored the
|
|
variable @code{program_invocation_name}.
|
|
|
|
@comment errno.h
|
|
@comment GNU
|
|
@deftypevar {char *} program_invocation_name
|
|
This variable's value is the name that was used to invoke the program
|
|
running in the current process. It is the same as @code{argv[0]}. Note
|
|
that this is not necessarily a useful file name; often it contains no
|
|
directory names. @xref{Program Arguments}.
|
|
|
|
This variable is a GNU extension and is declared in @file{errno.h}.
|
|
@end deftypevar
|
|
|
|
@comment errno.h
|
|
@comment GNU
|
|
@deftypevar {char *} program_invocation_short_name
|
|
This variable's value is the name that was used to invoke the program
|
|
running in the current process, with directory names removed. (That is
|
|
to say, it is the same as @code{program_invocation_name} minus
|
|
everything up to the last slash, if any.)
|
|
|
|
This variable is a GNU extension and is declared in @file{errno.h}.
|
|
@end deftypevar
|
|
|
|
The library initialization code sets up both of these variables before
|
|
calling @code{main}.
|
|
|
|
@strong{Portability Note:} If you want your program to work with
|
|
non-GNU libraries, you must save the value of @code{argv[0]} in
|
|
@code{main}, and then strip off the directory names yourself. We
|
|
added these extensions to make it possible to write self-contained
|
|
error-reporting subroutines that require no explicit cooperation from
|
|
@code{main}.
|
|
|
|
Here is an example showing how to handle failure to open a file
|
|
correctly. The function @code{open_sesame} tries to open the named file
|
|
for reading and returns a stream if successful. The @code{fopen}
|
|
library function returns a null pointer if it couldn't open the file for
|
|
some reason. In that situation, @code{open_sesame} constructs an
|
|
appropriate error message using the @code{strerror} function, and
|
|
terminates the program. If we were going to make some other library
|
|
calls before passing the error code to @code{strerror}, we'd have to
|
|
save it in a local variable instead, because those other library
|
|
functions might overwrite @code{errno} in the meantime.
|
|
|
|
@smallexample
|
|
#define _GNU_SOURCE
|
|
|
|
#include <errno.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
|
|
FILE *
|
|
open_sesame (char *name)
|
|
@{
|
|
FILE *stream;
|
|
|
|
errno = 0;
|
|
stream = fopen (name, "r");
|
|
if (stream == NULL)
|
|
@{
|
|
fprintf (stderr, "%s: Couldn't open file %s; %s\n",
|
|
program_invocation_short_name, name, strerror (errno));
|
|
exit (EXIT_FAILURE);
|
|
@}
|
|
else
|
|
return stream;
|
|
@}
|
|
@end smallexample
|
|
|
|
Using @code{perror} has the advantage that the function is portable and
|
|
available on all systems implementing @w{ISO C}. But often the text
|
|
@code{perror} generates is not what is wanted and there is no way to
|
|
extend or change what @code{perror} does. The GNU coding standard, for
|
|
instance, requires error messages to be preceded by the program name and
|
|
programs which read some input files should provide information
|
|
about the input file name and the line number in case an error is
|
|
encountered while reading the file. For these occasions there are two
|
|
functions available which are widely used throughout the GNU project.
|
|
These functions are declared in @file{error.h}.
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypefun void error (int @var{status}, int @var{errnum}, const char *@var{format}, @dots{})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @asuheap{} @asuintl{}}@acsafe{}}
|
|
@c Cancellation is disabled throughout the execution. It flushes stdout
|
|
@c and then holds a lock on stderr while printing the program name and
|
|
@c then running error_tail. The non-wide case just runs vfprintf; the
|
|
@c wide case converts the message to an alloca/malloc-allocated buffer
|
|
@c with mbsrtowcs, then prints it with vfwprintf. Afterwards,
|
|
@c print_errno_message calls strerror_r and fxprintf.
|
|
The @code{error} function can be used to report general problems during
|
|
program execution. The @var{format} argument is a format string just
|
|
like those given to the @code{printf} family of functions. The
|
|
arguments required for the format can follow the @var{format} parameter.
|
|
Just like @code{perror}, @code{error} also can report an error code in
|
|
textual form. But unlike @code{perror} the error value is explicitly
|
|
passed to the function in the @var{errnum} parameter. This eliminates
|
|
the problem mentioned above that the error reporting function must be
|
|
called immediately after the function causing the error since otherwise
|
|
@code{errno} might have a different value.
|
|
|
|
The @code{error} prints first the program name. If the application
|
|
defined a global variable @code{error_print_progname} and points it to a
|
|
function this function will be called to print the program name.
|
|
Otherwise the string from the global variable @code{program_name} is
|
|
used. The program name is followed by a colon and a space which in turn
|
|
is followed by the output produced by the format string. If the
|
|
@var{errnum} parameter is non-zero the format string output is followed
|
|
by a colon and a space, followed by the error message for the error code
|
|
@var{errnum}. In any case is the output terminated with a newline.
|
|
|
|
The output is directed to the @code{stderr} stream. If the
|
|
@code{stderr} wasn't oriented before the call it will be narrow-oriented
|
|
afterwards.
|
|
|
|
The function will return unless the @var{status} parameter has a
|
|
non-zero value. In this case the function will call @code{exit} with
|
|
the @var{status} value for its parameter and therefore never return. If
|
|
@code{error} returns the global variable @code{error_message_count} is
|
|
incremented by one to keep track of the number of errors reported.
|
|
@end deftypefun
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypefun void error_at_line (int @var{status}, int @var{errnum}, const char *@var{fname}, unsigned int @var{lineno}, const char *@var{format}, @dots{})
|
|
@safety{@prelim{}@mtunsafe{@mtasurace{:error_at_line/error_one_per_line} @mtslocale{}}@asunsafe{@asucorrupt{} @asuheap{} @asuintl{}}@acunsafe{@acucorrupt{/error_one_per_line}}}
|
|
@c The error_one_per_line variable is accessed (without any form of
|
|
@c synchronization, but since it's an int used once, it should be safe
|
|
@c enough) and, if this mode is enabled, static variables used to hold
|
|
@c the last printed file name and line number are accessed and modified
|
|
@c without synchronization; the update is not atomic and it occurs
|
|
@c before disabling cancellation, so it can be interrupted after only
|
|
@c one of the two variables is modified. After that, it's very much
|
|
@c like error.
|
|
|
|
The @code{error_at_line} function is very similar to the @code{error}
|
|
function. The only difference are the additional parameters @var{fname}
|
|
and @var{lineno}. The handling of the other parameters is identical to
|
|
that of @code{error} except that between the program name and the string
|
|
generated by the format string additional text is inserted.
|
|
|
|
Directly following the program name a colon, followed by the file name
|
|
pointer to by @var{fname}, another colon, and a value of @var{lineno} is
|
|
printed.
|
|
|
|
This additional output of course is meant to be used to locate an error
|
|
in an input file (like a programming language source code file etc).
|
|
|
|
If the global variable @code{error_one_per_line} is set to a non-zero
|
|
value @code{error_at_line} will avoid printing consecutive messages for
|
|
the same file and line. Repetition which are not directly following
|
|
each other are not caught.
|
|
|
|
Just like @code{error} this function only returned if @var{status} is
|
|
zero. Otherwise @code{exit} is called with the non-zero value. If
|
|
@code{error} returns the global variable @code{error_message_count} is
|
|
incremented by one to keep track of the number of errors reported.
|
|
@end deftypefun
|
|
|
|
As mentioned above the @code{error} and @code{error_at_line} functions
|
|
can be customized by defining a variable named
|
|
@code{error_print_progname}.
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypevar {void (*error_print_progname)} (void)
|
|
If the @code{error_print_progname} variable is defined to a non-zero
|
|
value the function pointed to is called by @code{error} or
|
|
@code{error_at_line}. It is expected to print the program name or do
|
|
something similarly useful.
|
|
|
|
The function is expected to be print to the @code{stderr} stream and
|
|
must be able to handle whatever orientation the stream has.
|
|
|
|
The variable is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypevar {unsigned int} error_message_count
|
|
The @code{error_message_count} variable is incremented whenever one of
|
|
the functions @code{error} or @code{error_at_line} returns. The
|
|
variable is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypevar int error_one_per_line
|
|
The @code{error_one_per_line} variable influences only
|
|
@code{error_at_line}. Normally the @code{error_at_line} function
|
|
creates output for every invocation. If @code{error_one_per_line} is
|
|
set to a non-zero value @code{error_at_line} keeps track of the last
|
|
file name and line number for which an error was reported and avoid
|
|
directly following messages for the same file and line. This variable
|
|
is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@noindent
|
|
A program which read some input file and reports errors in it could look
|
|
like this:
|
|
|
|
@smallexample
|
|
@{
|
|
char *line = NULL;
|
|
size_t len = 0;
|
|
unsigned int lineno = 0;
|
|
|
|
error_message_count = 0;
|
|
while (! feof_unlocked (fp))
|
|
@{
|
|
ssize_t n = getline (&line, &len, fp);
|
|
if (n <= 0)
|
|
/* @r{End of file or error.} */
|
|
break;
|
|
++lineno;
|
|
|
|
/* @r{Process the line.} */
|
|
@dots{}
|
|
|
|
if (@r{Detect error in line})
|
|
error_at_line (0, errval, filename, lineno,
|
|
"some error text %s", some_variable);
|
|
@}
|
|
|
|
if (error_message_count != 0)
|
|
error (EXIT_FAILURE, 0, "%u errors found", error_message_count);
|
|
@}
|
|
@end smallexample
|
|
|
|
@code{error} and @code{error_at_line} are clearly the functions of
|
|
choice and enable the programmer to write applications which follow the
|
|
GNU coding standard. @Theglibc{} additionally contains functions which
|
|
are used in BSD for the same purpose. These functions are declared in
|
|
@file{err.h}. It is generally advised to not use these functions. They
|
|
are included only for compatibility.
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void warn (const char *@var{format}, @dots{})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascuintl{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Just calls vwarn with the va_list.
|
|
The @code{warn} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (0, errno, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void vwarn (const char *@var{format}, va_list @var{ap})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascuintl{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c While holding stderr's recursive lock, it prints the programname, the
|
|
@c given message, and the error string with fw?printf's %m. When the
|
|
@c stream is wide, convert_and_print converts the format string to an
|
|
@c alloca/malloc-created buffer using mbsrtowcs and then calls fwprintf.
|
|
The @code{vwarn} function is just like @code{warn} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as a value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void warnx (const char *@var{format}, @dots{})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as warn, but without the strerror translation issues.
|
|
The @code{warnx} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (0, 0, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used. The difference to @code{warn} is that no error number
|
|
string is printed.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void vwarnx (const char *@var{format}, va_list @var{ap})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as vwarn, but without the strerror translation issues.
|
|
The @code{vwarnx} function is just like @code{warnx} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as a value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void err (int @var{status}, const char *@var{format}, @dots{})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascuintl{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as warn followed by exit.
|
|
The @code{err} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (status, errno, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used and that the program is exited even if @var{status} is zero.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void verr (int @var{status}, const char *@var{format}, va_list @var{ap})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascuintl{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as vwarn followed by exit.
|
|
The @code{verr} function is just like @code{err} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as a value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void errx (int @var{status}, const char *@var{format}, @dots{})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as warnx followed by exit.
|
|
The @code{errx} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (status, 0, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used and that the program is exited even if @var{status}
|
|
is zero. The difference to @code{err} is that no error number
|
|
string is printed.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void verrx (int @var{status}, const char *@var{format}, va_list @var{ap})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as vwarnx followed by exit.
|
|
The @code{verrx} function is just like @code{errx} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as a value of type @code{va_list}.
|
|
@end deftypefun
|