error(3)

NAME

   error,    error_at_line,    error_message_count,    error_one_per_line,
   error_print_progname - glibc error reporting functions

SYNOPSIS

   #include <error.h>

   void error(int status, int errnum, const char *format, ...);

   void error_at_line(int status, int errnum, const char *filename,
                      unsigned int linenum, const char *format, ...);

   extern unsigned int error_message_count;

   extern int error_one_per_line;

   extern void (*error_print_progname) (void);

DESCRIPTION

   error() is a general error-reporting function.  It flushes stdout,  and
   then  outputs  to  stderr  the  program  name, a colon and a space, the
   message specified by the printf(3)-style format string format, and,  if
   errnum  is  nonzero,  a second colon and a space followed by the string
   given by strerror(errnum).  Any arguments required  for  format  should
   follow  format  in  the  argument  list.  The output is terminated by a
   newline character.

   The program name printed by error() is the value of the global variable
   program_invocation_name(3).   program_invocation_name initially has the
   same value as main()'s argv[0].  The value  of  this  variable  can  be
   modified to change the output of error().

   If  status has a nonzero value, then error() calls exit(3) to terminate
   the program using the given value as the exit status.

   The error_at_line() function is exactly the same as error(), except for
   the  addition  of  the  arguments  filename  and  linenum.   The output
   produced is as for error(), except that  after  the  program  name  are
   written:  a  colon,  the  value  of filename, a colon, and the value of
   linenum.  The preprocessor values __LINE__ and __FILE__ may  be  useful
   when  calling  error_at_line(), but other values can also be used.  For
   example, these arguments could refer to a location in an input file.

   If the global variable error_one_per_line is set nonzero, a sequence of
   error_at_line()  calls with the same value of filename and linenum will
   result in only one message (the first) being output.

   The global variable error_message_count counts the number  of  messages
   that have been output by error() and error_at_line().

   If  the global variable error_print_progname is assigned the address of
   a function (i.e., is not NULL), then that function is called instead of
   prefixing  the  message  with the program name and colon.  The function
   should print a suitable string to stderr.

ATTRIBUTES

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(7).

   
   Interface        Attribute      Value                             
   
   error()          Thread safety  MT-Safe locale                    
   
   error_at_line()  Thread safety  MT-Unsafe race:                   
                                   error_at_line/error_one_per_line  
                                   locale                            
   
   The  internal error_one_per_line variable is accessed (without any form
   of synchronization, but since it's an int used once, it should be  safe
   enough)  and, if error_one_per_line is set nonzero, the internal static
   variables (not exposed to users) used to hold the last printed filename
   and  line number are accessed and modified without synchronization; the
   update is not atomic and it occurs before disabling cancellation, so it
   can  be  interrupted  only  after one of the two variables is modified.
   After that, error_at_line(3) is very much like error().

CONFORMING TO

   These functions and variables are GNU extensions,  and  should  not  be
   used in programs intended to be portable.

SEE ALSO

   err(3),   errno(3),   exit(3),  perror(3),  program_invocation_name(3),
   strerror(3)

COLOPHON

   This page is part of release 4.09 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
   https://www.kernel.org/doc/man-pages/.

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