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perror - sys_nerr-1 Be careful when directly accessing this...

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PERROR(3) Library functions 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 ; 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. The argument string s is printed first, then 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 non-erroneous 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
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Unformatted text preview: 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 per-ror() serves to translate this error code into human-readable form. Note that errno is undefined after a suc-cessful 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 ANSI C, BSD 4.3, POSIX, X/OPEN SEE ALSO strerror (3) May 16 1996 1...
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