How to implement shell output as a input of C language?

Question

For example, Guess I have a compiled c program, named as 'binaryOutput'. And in Unix environment, [root@blablabla ~ ] ./binaryOutput print out some result like this [0] [1] [0] [1] [1]

I want to using these result as the input of another c file.

In C lanugage, I can run the file.

system("./binaryOutput") ;

After the code, I want to add the numbers as an array's input. How can I do it?

You should look into popen() from here: lix.polytechnique.fr/~liberti/public/computing/prog/c/C/… — user2453382
– user2453382, Commented Mar 27, 2018 at 5:26
Possible duplicate of How can I run an external program from C and parse its output? — Lanting
– Lanting, Commented Mar 27, 2018 at 5:37
Would (from a shell): ./binaryOutput|myprog be acceptable? In myprog you just read stdin. It is the simplest way to do this. — cdarke
– cdarke, Commented Mar 27, 2018 at 6:33

Gerhardh · Accepted Answer · 2018-03-27 07:44:31Z

2

popen example. You can get the output of the command.

#include <stdio.h>

int main(void)
{
  FILE *fp=NULL;
  char line[1024];
  if ( (fp=popen("ls", "r"))==NULL )
  {
    return -1;
  }
  while( fgets(line, 1023, fp)!=NULL )
  {
    printf("read from popen:%s", line);
  }
  pclose(fp);
  return 0;
}

edited Mar 27, 2018 at 7:44

Gerhardh

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answered Mar 27, 2018 at 5:23

Junhee Shin

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5 Comments

user2453382 Over a year ago

Could you also describe how your code works? It looks like your program collects dir listing. That's not what OP is looking for. The question asks about executing any executables. Not a specific unix command. So tell us the generic approach.

Junhee Shin Over a year ago

replace "ls" to what you want. "./binaryOutput"

Jabberwocky Over a year ago

@MohammadRakibAmin ls is part of the set "any executables".

David C. Rankin Over a year ago

fgets(line, sizeof line, fp) -- there is no reason to reduce the size parameter to fgets by 1 as you do for scanf field-width modifier.

user2453382 Over a year ago

@Michael Walz I was unaware you have to figure out what 'set' does an input belongs to, then check if that 'set' covers your desired input. Would it not be more helpful to just mention your command goes here? I'm only pointing out ways to be more clear to OP's query.

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