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NAME | SYNOPSIS | DESCRIPTION | VERSIONS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
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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 * const sys_errlist[];
int sys_nerr;
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:
From glibc 2.19 to 2.31:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_BSD_SOURCE
The 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 ('\0')), 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;
use strerror(3) instead.
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 system 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.
Since glibc version 2.32, the declarations of sys_errlist and
sys_nerr are no longer exposed by <stdio.h>.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────┬───────────────┬─────────────────────┐
│Interface │ Attribute │ Value │
├──────────┼───────────────┼─────────────────────┤
│perror() │ Thread safety │ MT-Safe race:stderr │
└──────────┴───────────────┴─────────────────────┘
perror(), 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.
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 5.10 of the Linux man-pages project.
A description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2020-11-01 PERROR(3)
Pages that refer to this page: err(3), errno(3), error(3), fmtmsg(3), pmerrstr(3), psignal(3), sd_journal_print(3), stdio(3), strerror(3)
Copyright and license for this manual page
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