System() parameters C

Question

I've a problem with the system() function.

I want to create a little program which run a command x times.

The following code is to launch a command :

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

int main(int argc, char *argv[])
{
    char command[100];
    strcpy(command, "(time lance REF_CLIENT_FOUR002542_C FE-ERPCP-REF_CLIENT_FOUR.zip F > result.txt) 2> time.txt");
    system(command);
    return 0;
}

My command is working when I write it directly in my shell, but when I use this program I get this error:

./lance: [[: introuvable
./lance: [[: introuvable
./lance: [[: introuvable
./lance: [[: introuvable
./lance: erreur de syntaxe ligne 34: `(' inattendue

This error means:

./lance: [[: not found
./lance: syntax error at line 34 : '(' unexpected

I guess that system try to execute my command like time ./lance ..., but I want to run this like a command not a program so time lance ...

I've already tried to run this program without the loop, still the same.

I've also tried a simpler command like ls -l; that's working.

If anyone can help me, I'll be very thankful!

Edit : My purpose is to run a script many time to have data about execution's time, that's why I wrote this program.

Edit2: This is a part of my script "lance" :

if [[ $# -ne 3 ]] # 1st not found
 then
   echo "bla"
   exit 1
fi

if [[ ! -f ${1} ]] # 2nd not found
then
   echo "bla"
   exit 1
fi

if [[ ! -f ${2} ]] # 3rd not found
then
  echo "bla"
  exit 1
fi

if [[ "${3}" != "F" &&  "${3}" != "Z" ]] #4th not found
then
   echo "bla"
   exit 1
fi

if [[ -d TRAVAIL ]] # This is the line 34
then
  mv TRAVAIL TRAVAIL_$(date +%d%m%y%H%M%S)
fi

Edit3 : Thanks for alk who help me to find what was wrong is my code, I've added #!/bin/bash in the 1st line of my script and now it's working.

What happens if you type (time lance REF_CLIENT_FOUR002542_C FE-ERPCP-REF_CLIENT_FOUR.zip F > result.txt) 2> time.txt from the command line ? — Jabberwocky
– Jabberwocky, Commented May 4, 2016 at 9:11
Implementing your use-case in C seems a little bit like taking a sledgehammer to crack a nut. You want to have a look at some basic shell scripting. — alk
– alk, Commented May 4, 2016 at 9:14
Have you tried running your command the way that system() does? I.e. /bin/sh -c "(time lance ...)" - that may expose some assumptions you've made about $SHELL. — Toby Speight
– Toby Speight, Commented May 4, 2016 at 9:16
If you're using system(), you don't need fork(). The system() function essentially does a fork for you. — Steve Summit
– Steve Summit, Commented May 4, 2016 at 9:17
"but I want to run this like a command not a program so time lance ..." please excuse but I somewhat do under understand what you want to express. — alk
– alk, Commented May 4, 2016 at 9:17

unwind · Accepted Answer · 2016-05-04 09:19:19Z

1

You don't need to fork() when using system()! The latter is a much more high-level call, it will fork a shell and ask that to run the command.

answered May 4, 2016 at 9:19

unwind

402k64 gold badges492 silver badges620 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

alk Over a year ago

Without forking the program behaves differently, as the calls to system() would run in sequence, not in parallel.

alk Over a year ago

@ArthurDessez: "I removed fork()" So you also want to remove the wait()` as it most likely does not do what you expect. Please RTFM here: man7.org/linux/man-pages/man2/wait.2.html

alk · Accepted Answer · 2016-05-04 10:08:10Z

0

./lance: syntax error at line 34 : '(' unexpected

In script lance on line 34 there is an unexpected ( character.

To debug the script put this

set -x

as first statement into the script.

answered May 4, 2016 at 10:08

alk

71.2k10 gold badges112 silver badges274 bronze badges

3 Comments

Arthur Dessez Over a year ago

I've updated my code. The thing that I don't understand is when I run the script directly on the line command it's working but not with my program. I've use your tips to debug and every ./lance not found is during if at the beginning (I add this part of code in the first post)

alk Over a year ago

@ArthurDessez: The error ./lance: [[: introuvable does not mean "lance not found", but in file ./lance some [[ was "not found".

alk Over a year ago

@ArthurDessez: Make sure your script defines which shell it needs to run in. If you want the script to run using bash, put this #!/bin/bash as 1st line in the script. system() uses /bin/sh, the login you might run your test from perhaps uses a different one. Also you want to check if /bin/sh is a link, and to what.

Collectives™ on Stack Overflow

System() parameters C

2 Answers 2

2 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related