Replacing a Process Image

Ankur Garg — Fri, 15 Jan 2016 10:40:34 +0000

Replacing a Process Image
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- The exec function replaces current process with a new process.
- The path of new process is specified as argument to exec.
- It is defined in header :
#include
- Last argument of function should be NULL.
- It has 6 types of functions, whose prototype are :-
(i) Complete path is specified
int execl(const char * path, const char * arg0,const char * arg1,…,NULL);
(ii) If file is at one of default paths
int execlp(const char * file, const char * arg0,const char * arg1,…,NULL);
(iii) If arguments are given as an vector(array)
int execv(const char *path,char *const argv[]);
(iv) If arguments are given as an vector(array) and file is at one of default paths
int execvp(const char* file, char *const argv[]);
(v) int execle(const char *path, const char * arg0, const char * arg1,…,NULL, char *const envp[]);
(vi) int execve(const char *path, char *const argv[],char *const envp[] );

- The suffix p means to search PATH environmental variable.

- If the exec is executed successfully the statements after it will not be executed.
- It is because the current process is replaced.
- The arguments given to exec are used by main() function of new process as command line argument.
- If exec fails, it returns -1
- The open file descriptors remain open after the exec command.
- These file descriptors can be passed to exec as command and can be used by the replaced process to read/write from opened file.
- The argument is passed to exec as character.
- For this sprintf() is used.
- And for getting the file descriptors back , atoi() or integer typecasting can be used on the arguments of main().

Process replacement using execl

Joon Vichitra — Mon, 22 Sep 2014 13:09:46 +0000

RCS file: p_replace.c,v
Working file: p_replace.c
head: 1.2
branch:
locks: strict
access list:
symbolic names:
keyword substitution: kv
total revisions: 2; selected revisions: 2
description:
program to replace the child process using execl()
—————————-
revision 1.2
date: 2014/09/22 10:22:30; author: root; state: Exp; lines: +9 -1
use wait statement so that parent will wait till the child completed its execution
—————————-
revision 1.1
date: 2014/09/22 10:06:47; author: root; state: Exp;
Initial revision
=============================================================================

RCS file: child.c,v
Working file: child.c
head: 1.1
branch:
locks: strict
access list:
symbolic names:
keyword substitution: kv
total revisions: 1; selected revisions: 1
description:
sample program which replace the child when call by child through execl()
—————————-
revision 1.1
date: 2014/09/22 10:06:07; author: root; state: Exp;
Initial revision
=============================================================================

EmbLogic » process replacement

Replacing a Process Image

Process replacement using execl