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/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
