Re: How to execute a process in background by exec functions?

["John T. Williams" <jowillia@vt.edu>]

The single quotes need to be double quotes 
so the call should look like 

execl("/bin/ls", "ls", 0);  





On Sun, 2004-04-11 at 13:37, Jose Luis Alarcon Sanchez wrote:
> ---- Begin Original Message ----
> running a process in the background simply means not waiting for it to
> complete.  So a parent process that wanted to make a child process run
> ls in the ´background¡ would do something like this: (again this should
> be treated as sudo code that just looks a lot like C)
> 
> _______________________CODE__________________
> int
> main (int argC, char** argV) {
> int bg = 1;  // test condition for running in the background
> int pid; 
> int status;
> 
> if( (pid = fork()) ==  0 )   {
> 	/* child code starts here */
> 	execl(´/bin/ls¡, ´/bin/ls¡, 0 ); 
> 
> } else {
> 	/* this is the critical point, if you call wait, the parent 	process
> stops until the child process returns, which would be fg 	behavior (at
> least in a shell).  If the 
> 	parent doesn't call wait (or waitpid), then both parent and 	child will
> run at the same time. (i.e. The child runs in the 	background */ 
> 	if( !bg) {  
> 		wait(&status);
> 	}
> 	/* Parent Code Starts here */
> }
> 
> return 0;
> }
> _________________________END CODE_____________________
> 
> There are also considerations about input and output, and bringing the
> process from the background to the forground, and sending it back into
> the background, and so forth.  If your really interested in how this
> works and how to address the more complex issues, I suggest that you
> read the source code for GNU BASH, which is freely available (at this
> point everyone must think I'm a spokes person for GNU)  or Read the
> O'Reilly books "Learning the bash Shell, 2nd Edition", and "Practical
> C Programming, 3rd Edition"
> ---- End Original Message ----
> 
> 
>   Hi John.
> 
>   I am trying compile the code you paste in your message,
> but i get an error with the line
> 
> execl(´/bin/ls¡, ´/bin/ls¡, 0 );
> 
> Process_Exec.c:15:11: warning: character constant too long for its type
> Process_Exec.c: In function `main':
> Process_Exec.c:15: error: `bin' undeclared (first use in this function)
> Process_Exec.c:15: error: (Each undeclared identifier is reported only
> once
> Process_Exec.c:15: error: for each function it appears in.)
> Process_Exec.c:15: error: stray '\241' in program
> Process_Exec.c:15: error: `ls' undeclared (first use in this function) 
> 
>   I'm afraid that it is for the character before the '/',
> i can't get it with any key. But i am not sure, i am a very 
> newbie C programmer.
> 
>   I hope you can help me.
> 
>   Thanks, very much, in advance.
> 
>   Regards.
> 
>   Jose.
> 
> 
> http://www.lordofunix.org
> 
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