C process control refers to a group of functions in the standard library of the C programming language implementing basic process control operations.[1][2] The process control operations include actions such as termination of the program with various levels of cleanup, running an external command interpreter or accessing the list of the environment operations.
Overview of functions
editThe process control functions are defined in the stdlib.h header (cstdlib header in C++).
| Function | Description | |
|---|---|---|
| Terminating a program |
abort
|
causes abnormal program termination (without cleaning up) |
exit
|
causes normal program termination with cleaning up | |
_Exit
|
causes normal program termination without cleaning up (C99) | |
atexit
|
registers a function to be called on exit() invocation | |
quick_exit
|
causes normal program termination without cleaning up, but with IO buffers flushed (C11) | |
at_quick_exit
|
registers a function to be called on quick_exit() invocation | |
| Communicating with the environment |
getenv
|
accesses the list of the environment variables |
system
|
calls the host environment's command processor |
Example
editThe following is an example of communicating with the system environment in C.
#include <stdio.h>
#include <stdlib.h>
int main() {
char* path = getenv("PATH");
if (!path) {
fprintf(stderr, "PATH environment variable not found.\n");
} else {
printf("PATH variable: %s\n", path);
}
printf("Listing current directory contents using system(\"ls\"):\n");
int ret = system("ls");
if (ret == -1) {
fprintf(stderr, "system() call failed!");
}
return 0;
}
References
edit- ^ Crawford, Tony; Peter Prinz (December 2005). C in a Nutshell. §16.11 – Process Control: O'Reilly. p. 618. ISBN 0-596-00697-7.
{{cite book}}: CS1 maint: location (link) - ^ ISO/IEC 9899:1999 specification (PDF). p. 315, § 7.20.4 "Communication with the environment". Retrieved 25 November 2011.
External links
edit
Wikibooks has a book on the topic of: C Programming/C Reference
