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perror(3c) [sunos man page]

perror(3C)																perror(3C)

NAME
perror, errno - print system error messages SYNOPSIS
#include <stdio.h> void perror(const char *s); #include <errno.h> int errno; The perror() function produces a message on the standard error output (file descriptor 2) describing the last error encountered during a call to a system or library function. The argument string s is printed, followed by a colon and a blank, followed by the message and a NEW- LINE character. If s is a null pointer or points to a null string, the colon is not printed. The argument string should include the name of the program that incurred the error. The error number is taken from the external variable errno, which is set when errors occur but not cleared when non-erroneous calls are made. See intro(2). In the case of multithreaded applications, the -mt option must be specified on the command line at compilation time (see threads(5)). When the -mt option is specified, errno becomes a macro that enables each thread to have its own errno. This errno macro can be used on either side of the assignment as though it were a variable. USAGE
Messages printed from this function are in the native language specified by the LC_MESSAGES locale category. See setlocale(3C). See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ intro(2), fmtmsg(3C), gettext(3C), setlocale(3C), strerror(3C), attributes(5), standards(5), threads(5) 31 Mar 2005 perror(3C)

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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 *sys_errlist[]; int sys_nerr; int errno; Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sys_errlist, sys_nerr: _BSD_SOURCE DESCRIPTION
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 ('')) 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 num- ber 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. CONFORMING TO
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. 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 3.25 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)
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