[Quick question]Problem with execl and GREP

pfpietro · 08-31-2012, 04:04 PM

Guys, I have the following code

Code:

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>

void read2();
main(int argc, char** argv)
{
int pid,status;
	pid=fork();
	if ( pid == 0 )
	{
		read2(argv[1], argv[2]);
		exit(0);	
	}
	else
	wait(&status);
}

void read2(char * file, char * stringa)
{
	printf("%s, %s\n",file, stringa);
	execl("/usr/bin/grep", "grep", "-c", stringa, file, (char *)0);
		
}

Why I don't see any outputs on the screen when I run my program ?
usying any .txt file I should get on stdout ( screen ) the number of lines that "stringa" shows up. But I don't.

What am I doing wrong ?

billyoc · 08-31-2012, 05:09 PM

Quote:

Originally Posted by pfpietro

Guys, I have the following code

Code:

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>

void read2();
main(int argc, char** argv)
{
int pid,status;
	pid=fork();
	if ( pid == 0 )
	{
		read2(argv[1], argv[2]);
		exit(0);	
	}
	else
	wait(&status);
}

void read2(char * file, char * stringa)
{
	printf("%s, %s\n",file, stringa);
	execl("/usr/bin/grep", "grep", "-c", stringa, file, (char *)0);
		
}

Why I don't see any outputs on the screen when I run my program ?
usying any .txt file I should get on stdout ( screen ) the number of lines that "stringa" shows up. But I don't.

What am I doing wrong ?

Wow, it works fine here. I ran it against its own source file:
./test1 test1.c read2
and got:
test1.c, read2
3

pfpietro · 08-31-2012, 05:59 PM

... I don't know what to do...
I've tryied everything

pfpietro · 08-31-2012, 06:46 PM

Ok, the perror says "No such file or directory"

I don't understand because when I launch the terminal and use "ls" to list all the files, of course I see the file I'm calling the program with. However even if I change the file name for another one or either the file source I still get the same error.

grep works like that, right ? GREP -C PATTERN FILE

so my command line is execl("usr/bin/grep", "grep", "-c", stringa, file, NULL); its supposed to execute GREP -C STRING FILE
but I still get the error.

does anyone can explain me why I'm so blind that I can't see where the problem is ?

pfpietro · 09-02-2012, 10:21 AM

anyone ?

firstfire · 09-02-2012, 02:40 PM

Hi.

Did you tried to run

Code:

$ which grep
/bin/grep

??

firstfire · 09-03-2012, 01:10 PM

Well, I meant that /usr/bin/grep is a wrong path to grep binary. It should probably be /bin/grep.