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Top Forums UNIX for Dummies Questions & Answers [Quick question]Problem with execl and GREP Post 302694959 by pfpietro on Friday 31st of August 2012 07:22:12 PM
Old 08-31-2012
[Quick question]Problem with execl and GREP

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("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 ? A friend of mine tryied in his computer and it worked. Why it doesn't work in mine ?
 

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Ns_Exec(3aolserver)					   AOLserver Library Procedures 				       Ns_Exec(3aolserver)

__________________________________________________________________________________________________________________________________________________

NAME
Ns_ExecArgblk, Ns_ExecArgv, Ns_ExecProc, Ns_ExecProcess, Ns_Fork, Ns_GetEnviron, Ns_WaitForProcess, Ns_WaitProcess, ns_fork - External process execution SYNOPSIS
#include "ns.h" int Ns_ExecArgblk(char *exec, char *dir, int fdin, int fdout, char *args, Ns_Set *env) int Ns_ExecArgv(char *exec, char *dir, int fdin, int fdout, char **argv, Ns_Set *env) int Ns_ExecProc(char *exec, char **argv) int Ns_ExecProcess(char *exec, char *dir, int fdin, int fdout, char *args, Ns_Set *env) int Ns_Fork(void) char **Ns_GetEnviron(void) int Ns_WaitForProcess(int pid, int *statusPtr) int Ns_WaitProcess(int pid) int ns_fork(void) _________________________________________________________________ DESCRIPTION
These functions handle fork and exec operations. See files: nsd/exec.c, nsd/tclenv.c and nsthread/fork.c. Ns_ExecArgblk(exec, dir, fdin, fdout, args, env) Executes a command in a child process. Return process id of child process exec'ing the command or -1 on failure. Provides extended error checking and error messages. Ns_ExecArgv(exec, dir, fdin, fdout, argv, env) Execute a command in a child process using fork(2) and execve(2), returns the process id of child process exec'ing the command or -1 on failure. The child sends an extended error message to the parent. Ns_ExecProc(exec, argv) Executes a command in a child process. Returns the process id of the child process exec'ing the command or -1 on failure. Simpli- fies call to Ns_ExecArgv. Ns_ExecProcess(exec, dir, fdin, fdout, args, env) Executes a command in a child process. Returns the process id of the child process exec'ing the command or -1 on failure. Calls Ns_ExecArgblk with same arguments. Ns_Fork() Posix style fork(), using fork1() on Solaris if needed. See fork(2) man page. Calls ns_fork. Ns_GetEnviron() Returns pointer to the environment vector. Ns_WaitForProcess(pid, statusPtr) Wait for child process. Returns NS_OK on success, or NS_ERROR on failure. *statusPtr is set to the exit code of the child process. Ns_WaitProcess(pid) Wait for child process. Calls Ns_WaitForProcess with NULL statusPtr. Returns NS_OK on success, or NS_ERROR on failure. ns_fork() Posix style fork(), using fork1() on Solaris if needed. SEE ALSO
nsd(1), info(n) KEYWORDS
AOLserver 4.0 Ns_Exec(3aolserver)
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