SIMPLE SOLUTIONS

PERROR(3) - man page online | library functions

Print a system error message.

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2015-07-23
PERROR(3)                           Linux Programmer's Manual                           PERROR(3)

NAME perror - print a system error message
SYNOPSIS #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: _BSD_SOURCE
DESCRIPTION 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 cur‐ rent 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 func‐ tions 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 exam‐ ple because it internally used some other library function that failed. Thus, if a fail‐ ing call is not immediately followed by a call to perror(), the value of errno should be saved.
ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌──────────┬───────────────┬─────────────────────┐ │Interface │ Attribute │ Value │ ├──────────┼───────────────┼─────────────────────┤ │perror() │ Thread safety │ MT-Safe race:stderr │ └──────────┴───────────────┴─────────────────────┘
CONFORMING TO 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.
NOTES The externals sys_nerr and sys_errlist are defined by glibc, but in <stdio.h>.
SEE ALSO err(3), errno(3), error(3), strerror(3)
COLOPHON This page is part of release 4.04 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 http://www.kernel.org/doc/man-pages/.
2015-07-23 PERROR(3)
This manual Reference Other manuals
perror(3) referred by af_error(3) | aufs(5) | err(3) | errno(2freebsd) | errno(3) | error(3) | errormsg(3pub) | explain(3) | explain_lca2010(1) | fmtmsg(3) | genders_errnum(3) | intro(2freebsd) | lam-helpfile(5) | pmErrStr(3) | psignal(3) | pvm_perror(3PVM) | rmt-dump(8) | rmt-tar(8) | sd_journal_print(3) | strerror(3)
refer to attributes(7) | err(3) | errno(3) | error(3) | feature_test_macros(7) | strerror(3)