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

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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. Tobeo fmost 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 [] indexedby errno
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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 &lt;errno.h&gt; .) 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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This note was uploaded on 10/05/2009 for the course COMP 2510 taught by Professor A during the Spring '06 term at BC.

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