CODEWITHSUNDEEP
c
user1089679
user1089679

Reputation: 2368

Confusion in Run a System Command and Get Output From Console

Here I got one program from somewhere to read output of a system call from the console. But to fetch error messages I used 2>&1 in fp = popen("ping 4.2.2.2 2>&1", "r"); this line instead of fp = popen("ping 4.2.2.2", "r");

So could anybody explain me Whats the significant of 2>&1 in above line.

Here is my code.

#include <stdio.h>
#include <stdlib.h>


int main( int argc, char *argv[] )
{

  FILE *fp;
  int status;
  char path[1035];

  /* Open the command for reading. */
  fp = popen("ping 4.2.2.2 2>&1", "r");
  if (fp == NULL) {
    printf("Failed to run command\n" );
    exit;
  }

  /* Read the output a line at a time - output it. */
  while (fgets(path, sizeof(path)-1, fp) != NULL) {
    printf("%s", path);
  }

  /* close */
  pclose(fp);

  return 0;
}

Upvotes: 2

Views: 203

Answers (1)

Sangeeth Saravanaraj
Sangeeth Saravanaraj

Reputation: 16597

0=stdin ; 1=stdout ; 2=stderr

If you do 2>1 that will redirect all the stderr to a file named 1. To actually redirect stderr to stdout you need to use 2>&1. &1 means passing the handle to the stdout.

This has been discussed here in detail.

Upvotes: 1

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