Latest revision as of 08:59, 17 December 2022

There are several ways of creating a new process.

Most used:
- fork system call family ("clone" a runnning process to two running instances of the same code)
- exec system call family (Execute a file)
But also:
- clone system call (Like fork - but more advanced)
- system and popen system call (Can give security issues)

Advanced

prctl

prctl - operations on a process

// Changing the name of running proces
#include <sys/prctl.h>
...
    prctl(PR_SET_NAME, "newname");
...

Links

Creating processes

@@ Line 1: / Line 1: @@
-{{TOCright}}
+There are several ways of creating a new process.
-'''fork()''' is one of several functions to "spawn" a process
+*Most used:
-=Use of fork=
+**[[fork system call]] family  ("clone" a runnning process to two running instances of the same code)
-fork() creates a new process by duplicating the calling process.  The new process is referred to as the child process.  The calling process is referred to as the parent process.
+**[[exec system call]] family (Execute a file)
-*PID - Process ID - the ID of a running process
+*But also:
-*PPID - Parent Process ID - default the ID of the process that created this process or 1 if the parent died.
+**[[clone system call]] (Like [[fork system call|fork]] - but more advanced)
-<source lang=c line>
+**[[system and popen system call]]  (Can give security issues)
-#include <stdio.h>
+=Advanced=
-#include <sys/types.h>
-#include <unistd.h>
-int main(void) {
-        printf("I am parent - my PPID is %d and my PID is %d\n", getppid(), getpid() );
-        if (fork() == 0) {
-                printf("I am child  - my PPID is %d and my PID is %d\n", getppid(), getpid() );
-                printf("Child  dying\n");
-                return(0);
-        }
-        printf("parent dying\n");
-        return(0);
-}
-</source>
-=Example of creating a daemon in Linux=
-{{:Daemon linux}}
-=Example of creating several processes=
-See same example in [[Bash processes#example|bash]]
-<source lang=c line>
-#include <stdio.h>
-#include <sys/types.h>
-#include <unistd.h>
-#include <wait.h>
-void childprocess(char *name, int count_to) {
-        int counter = 0;
-        printf("My name is %s and my PID is %d\n", name, getpid());
-        while (counter < count_to) {
-                sleep(1);
-                counter = counter +1;
-                printf("%s counted to %i\n", name, counter);
-        }
-        printf("%s signing off\n", name);
-}
-int main(void) {
-        int wstatus; // Used by c wait function
-        printf("I am the main function and my PID is %i\n", getpid());
-        if (fork() == 0) { // fork returns 0 for child
-                childprocess("Hans", 5);
-                return(0);      // Child process finished
-        }
-        if (fork() == 0) {
-                childprocess("Ulla", 3);
-                return(0);
-        }
-        while(wait(&wstatus) > 0);
-        printf("Main signing off\n");
-        return(0);
-}
-</source>
-=Advance=
 ==prctl==
 prctl - operations on a process
@@ Line 79: / Line 17: @@
 ...
 </source>
+=Links=
+*[http://boron.physics.metu.edu.tr/ozdogan/SystemsProgramming/week4/node8.html Creating processes]
+[[Category:Linux]][[Category:C]]

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Difference between revisions of "C processes in Linux"

Latest revision as of 08:59, 17 December 2022

Advanced

prctl

Links