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Asked: 2026-06-15T11:22:08+00:00

I have two programs ( Prog1.c and Prog2.c ) written in C and each

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I have two programs (Prog1.c and Prog2.c) written in C and each of them take one command line argument.

Prog1.c takes a file name as argument , reads content from file and outputs it on the STDOUT (standard output) screen. Prog2.c takes data as argument and does some operation. I want to redirect output of Prog1.c to Prog2.c as input.

I have tried following bash script which gives me error

#!/bin/bash
prog2 "`prog1 file.txt`"

I have also tried without quotes and in both cases, it gives me following error.

Prog2:: argument list too long.
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1 Answer

  1. Editorial Team

    To get the output of a command as a parameter for another command you can use backticks:

    prog2 "`prog1 file.txt`"

    or use $() (I believe this is a more preferred way for bash):

    prog2 "$(prog1 file.txt)"

    If you want to use the STDOUT of prog1 as STDIN for prog2 use the | (pipe) operator:

    prog1 | prog2

    Note: When you want to use pipes, you need to modify the code of prog2, as it needs to read from STDIN instead of the command arguments (argv of the main() function). See How to read a line from the console in C? for an example on how to do this.

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