HP-UX Reference (11i v1 05/09) - 3 Library Functions N-Z (vol 7)

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perror(3C) perror(3C)
NAME
perror(), strerror(), errno, sys_errlist, sys_nerr - system error messages
SYNOPSIS
#include <stdio.h>
void perror(const char *s);
#include <string.h>
char *strerror(int errnum);
#include <errno.h>
extern char *sys_errlist[ ];
extern int sys_nerr;
Obsolescent Interface
#include <string.h>
int strerror_r(int errnum, char *buffer, int buflen);
DESCRIPTION
perror() writes a language-dependent message to the standard error output, describing the last error
encountered during a call to a system or library function. The argument string s is printed first, followed
by a colon, a blank, the message, and a new-line. To be most useful, the argument string should include the
name of the program that incurred the error. The error number is taken from the symbol
errno
, which is
set when errors occur but not cleared when non-erroneous calls are made. The contents of the message is
identical to those returned by the
strerror() function with errno as the argument. If given a
NULL
string, the perror() function prints only the message and a new-line.
To simplify variant formatting of messages, the strerror() function and the sys_errlist array of
message strings are provided. The strerror() function maps the error number in errnum to a
language-dependent error message string and returns a pointer to the string. The message string is
returned without a new-line. errno can be used as an index into sys_errlist to get an untranslated
message string without the new-line. sys_nerr is the largest message number provided for in the table;
it should be checked because new error codes might be added to the system before they are added to the
table. strerror() must be used to retrieve messages when translations are desired.
Obsolescent Interface
strerror_r() handles system error messages.
EXTERNAL INFLUENCES
Environment Variables
The language of the message returned by strerror() and printed by perror() is specified by the
LANG environment variable. If the language-dependent message is not available, or if
LANG is not set or is
set to the empty string, the default version of the message associated with the "C" language (see lang(5)) is
used.
International Code Set Support
Single- and multi-byte character code sets are supported.
RETURN VALUE
perror() returns no value.
If the errnum message number is valid, strerror() returns a pointer to a language-dependent message
string. The array pointed to should not be modified by the program, and might be overwritten by a subse-
quent call to the function. If a valid errnum message number does not have a corresponding language-
dependent message, strerror() uses errnum as an index into sys_errlist to get the message
string. If the errnum message number is invalid, strerror() returns a pointer to a NULL string.
WARNINGS
The return value for strerror() points to data whose content is overwritten by subsequent calls to
strerror() from the same thread.
Section 3−−648 Hewlett-Packard Company − 1 − HP-UX 11i Version 1: September 2005