problem with "touch" command in c program

Hi,
I am working with c program that uses "touch" unix command. But, the command executes only in the second time I run the program. I tried extracting the command in a separate file and the other code in another file and running them separately, and that worked. I wonder why when I join them in one programe not working.

The command code:

Code:

---

#include <stdlib.h>

int main (void)
{
  system (" touch file ");
  return 0;
}

---

This is part of the code: where I use popen() function for paths of files and implemeting "touch" command for each path:

Code:

---

while (1)
{
  if (fgets (l, 260, ptr) == NULL)// get the path of the first file
      break;
  l [strlen (l) -1] = '\0';// convert it to string

  strcpy (command, "touch ");// using touch command
  strcat (command, l);
  system (command);

  fp = open (l, O_RDONLY);// Then opening the file

  if (fp == -1)
  {
      printf("Could not open file \n");
      exit(1);
  }
}

---

I need to use touch command for each file before opening it

Wouldn't it be easier to write a bash script?

If no-one is forcing you to use touch then you should definitely think about using fopen with a+ or open with O_CREAT. You could also break out the caveman debugging and printf the variable command to see what's going on.

Quote:

---

Originally Posted by sand_man

Wouldn't it be easier to write a bash script?

---

Well, it is just "touch command" from unix that I want to implement for the files before opening them, and all the other stuff in the program are purely c functions. So I think, it is better to do it in c; including unix command

Quote:

---

Originally Posted by valis

If no-one is forcing you to use touch then you should definitely think about using fopen with a+ or open with O_CREAT. You could also break out the caveman debugging and printf the variable command to see what's going on.

---

The variable command is fine, as I said: when running the command separately it works fine, but running the whole programe twice (no sparation):

./prog.exe -- the command not working
./prog.exe -- the command working

Try to do some actual error checking. See what the system() function is returning for one thing. Make sure all your buffers are big enough.

This is not converting l to a string:

Code:

---

l [strlen (l) -1] = '\0';// convert it to string

---

It's already a string, you're just getting rid of the newline at the end. Your method is flawed though. Input a line longer than 259 characters and you'll see.

While we're talking about l, change the name. l looks way too much like the number 1 and can lead to some funky bugs.

Also, I prefer to see:

Code:

---

sprintf(command, "touch %s", l);

---

instead of:

Code:

---

  strcpy (command, "touch ");// using touch command
  strcat (command, l);

---

1. Show us how you declared your arrays - did you declare them at all, or are they just char pointers?
2. Rename your 'l' array to be something more meaningful. A single lower-case "L" is very hard to tell from numeric 1, and in many places you can use either and not get a warning from the compiler.

Quote:

---

Originally Posted by itsme86

Try to do some actual error checking. See what the system() function is returning for one thing. Make sure all your buffers are big enough.

---

The system function returns what I want (excatly), I printf the command and it is fine.
Also, I noticed that "sometimes" the program implements the command after the second running and sometimes after the third.
When the program works fine after the second or third running is that mean there is some errors in the code, or some confliction between the code and system call ? ( I don't know :( )

Quote:

---

Originally Posted by itsme86

This is not converting l to a string:

Code:

---

l [strlen (l) -1] = '\0';// convert it to string

---

It's already a string, you're just getting rid of the newline at the end. Your method is flawed though. Input a line longer than 259 characters and you'll see.

While we're talking about l, change the name. l looks way too much like the number 1 and can lead to some funky bugs.

Also, I prefer to see:

Code:

---

sprintf(command, "touch %s", l);

---

instead of:

Code:

---

  strcpy (command, "touch ");// using touch command
  strcat (command, l);

---

---

Thanks :) :) :)

Quote:

---

Originally Posted by Salem

1. Show us how you declared your arrays - did you declare them at all, or are they just char pointers?

---

They are not pointers
char L [260], command [280]

Quote:

---

The system function returns what I want (excatly)

---

What exactly might that be?

If you're going to be vague and mysterious, at least post your whole code so some of us can see what's going on.

Out of curiosity, why is it that you have to use "touch"?