| NAME | SYNOPSIS | DESCRIPTION | CONFORMING TO | NOTES | SEE ALSO | COLOPHON | The Linux Programming Interface |
PERROR(3) Linux Programmer's Manual PERROR(3)
perror - print a system error message
#include <stdio.h>
void perror(const char *s);
#include <errno.h>
const char *sys_errlist[];
int sys_nerr;
int errno;
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sys_errlist, sys_nerr: _BSD_SOURCE
The routine perror() produces a message on the standard error output,
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 ('\0')) the
argument string s is printed, followed by a colon and a blank. Then the
message and a new-line.
To be of most use, the argument string should include the name of the function
that incurred the error. The error number is taken from the external variable
errno, which is set when errors occur but not cleared when successful calls
are made.
The global error list sys_errlist[] 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[].
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 library 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.
The function perror() and the external errno (see errno(3)) conform to C89,
C99, 4.3BSD, POSIX.1-2001. The externals sys_nerr and sys_errlist conform to
BSD.
The externals sys_nerr and sys_errlist are defined by glibc, but in <stdio.h>.
err(3), errno(3), error(3), strerror(3)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
2007-07-26 PERROR(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface