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() 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

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       information  about  reporting  bugs,  and  the  latest  version  of  this   page,   can   be   found   at
       https://www.kernel.org/doc/man-pages/.