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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |ATTRIBUTES |STANDARDS |SEE ALSO |COLOPHON | |
error(3) Library Functions Manualerror(3)error, error_at_line, error_message_count, error_one_per_line, error_print_progname - glibc error reporting functions
Standard C library (libc,-lc)
#include <error.h>void error(intstatus, interrnum, const char *format, ...);void error_at_line(intstatus, interrnum, const char *file,unsigned intline, const char *format, ...);extern unsigned interror_message_count;extern interror_one_per_line;extern typeof(void (void)) *error_print_progname;
error() is a general error-reporting function. It flushesstdout, and then outputs tostderr the program name, a colon and a space, the message specified by theprintf(3)-style format stringformat, and, iferrnum is nonzero, a second colon and a space followed by the string given bystrerror(errnum). Any arguments required forformat should followformat in the argument list. The output is terminated by a newline character. The program name printed byerror() is the value of the global variableprogram_invocation_name(3).program_invocation_name initially has the same value asmain()'sargv[0]. The value of this variable can be modified to change the output oferror(). Ifstatus has a nonzero value, thenerror() callsexit(3) to terminate the program using the given value as the exit status; otherwise it returns after printing the error message. Theerror_at_line() function is exactly the same aserror(), except for the addition of the argumentsfile andline. The output produced is as forerror(), except that after the program name are written: a colon, the value offile, a colon, and the value ofline. The preprocessor values__LINE__and__FILE__may be useful when callingerror_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 variableerror_one_per_line is set nonzero, a sequence oferror_at_line() calls with the same value offile andline will result in only one message (the first) being output. The global variableerror_message_count counts the number of messages that have been output byerror() anderror_at_line(). If the global variableerror_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 tostderr.
For an explanation of the terms used in this section, seeattributes(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 internalerror_one_per_line variable is accessed (without any form of synchronization, but since it's anint used once, it should be safe enough) and, iferror_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 cancelation, so it can be interrupted only after one of the two variables is modified. After that,error_at_line() is very much likeerror().
GNU.
err(3),errno(3),exit(3),perror(3),program_invocation_name(3),strerror(3)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-06-05error(3)Pages that refer to this page:err(3), errno(3), perror(3), strerror(3), sysexits.h(3head)
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HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |