Copyright (c) 1994 Michael Haardt (email@example.com), 1994-06-04 Copyright (c) 1995 Michael Haardt (firstname.lastname@example.org), 1995-03-16 Copyright (c) 1996 Andries Brouwer (email@example.com), 1996-01-13 %%%LICENSE_START(GPLv2+_DOC_FULL) This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The G...
NAMEperror - print a system error message
void perror(const char *s);
const char * const sys_errlist;
int errno; /* Not really declared this way; see errno(3) */
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sys_errlist, sys_nerr: _BSD_SOURCE
DESCRIPTIONThe perror() function produces a message on standard error describing the last error encountered during a call to a system or library function.
First (if s is not NULL and *s is not a null byte (aq\0aq)), the argument string s is printed, followed by a colon and a blank. Then an error message corresponding to the current value of errno and a new-line.
To be of most use, the argument string should include the name of the function that incurred the error.
The global error list sys_errlist, which can be indexed by errno, can be used to obtain the error message without the newline. The largest message number provided in the table is sys_nerr-1. Be careful when directly accessing this list, because new error values may not have been added to sys_errlist. The use of sys_errlist is nowadays deprecated.
When a system call fails, it usually returns -1 and sets the variable errno to a value describing what went wrong. (These values can be found in <errno.h>.) Many library functions do likewise. The function perror() serves to translate this error code into human-readable form. Note that errno is undefined after a successful sysme call or library function call: this call may well change this variable, even though it succeeds, for example because it internally used some other library function that failed. Thus, if a failing call is not immediately followed by a call to perror(), the value of errno should be saved.
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
|perror()||Thread safety||MT-Safe race:stderr|
CONFORMING TOperror(), errno: POSIX.1-2001, POSIX.1-2008, C89, C99, 4.3BSD.
The externals sys_nerr and sys_errlist derive from BSD, but are not specified in POSIX.1.