How to translate execution commands from bash script to C? or How to properly use popen() in "W" mode? -

hey all. i'm trying translate simple bash script executes program (called pdb2gmx) c commands can include function in larger program, i'm having trouble making happen.

the bash script:

#!/bin/sh /usr/local/gromacs/bin/pdb2gmx -f ${1}.pdb -o ${1}.gro -p ${1}.top << eof 14 6 

so what's going when running program, stops , asks user input @ 2 separate points, 1 right after other. in bash script, putting down 14 , 6 seems fulfill input requirement, can't seem pull off same trick in c (also, i'm not sure eof doing there, i'm following else's example that, , script won't work without it).

this have far in c:

#include <stdio.h> #include <stdlib.h>  int main() {     file * pdb2gmx;     pdb2gmx = popen( "pdb2gmx -f 1beo.pdb -o 1beo.gro -p 1beo.top" , "w" );     fprintf( pdb2gmx, "eof" );     fprintf( pdb2gmx, "14" );     fprintf( pdb2gmx, "6" );     pclose( pdb2gmx ); } 

but when code executed pdb2gmx hangs @ first point needs user input. missing?

my sense c program hanging on execution of popen line, , never getting fprintf lines, thought popen mode set "w" treat returned stream user input, i'm pretty confused.

you need add newlines (\n) end of fprintf strings...