#include <stdio.h>
#include <string.h>

int main() {
    /* simulation: calling an external Perl module */
    char *cmd = "/usr/bin/perl -e ' print q{PerlEcho: }, join(q{, },@ARGV), qq{\n} '";

    /* first example: system() */
    char sys_cmd[300]; /* hey, just a demo ... */
    strcpy(sys_cmd, cmd);
    strcat(sys_cmd, " par1 par2 par3 its the 'system()' call "); 
    /* a realistic example would redirect STDOUT and STDERR into files  */
    /* e.g:  strcat(sys_cmd," par1 par2  >output.1  2>output.2");      */
    /* (shell-interpreted: standard disclaimers apply) */
    printf("Calling perl via system():\n>>>");
    fflush(stdout);
    system(sys_cmd); /* todo: check result */ 


    /* second example: popen() */
    char ppn_cmd[300];
    strcpy(ppn_cmd, cmd);
    strcat(ppn_cmd, " now via 'popen()' ");
    printf("Calling perl via popen():\n>>>");

    FILE *fh = popen(ppn_cmd, "r"); /* read-only for now */
    if ( fh ) {
        char buffer[101];
        while( !feof(fh) ) {
          int len = fread(buffer, 1, 100, fh);
          if ( len>0 ) {
               buffer[len] = '\0';
               printf("%d: %s",len,buffer);
          }
        }
        if ( pclose(fh) ) perror("ERROR - Failed to close pipe properly");
    } else {
        perror("cannot popen");
        printf("ERROR - cannot run popen(%s,\"r\",)\n", ppn_cmd);
    }
    
    return 0;
}

/*
   pb:sopw > gcc sys_n_popen.c && a.out
   Calling perl via system():
   >>>PerlEcho: par1, par2, par3, its, the, system(), call
   Calling perl via popen():
   >>>28: PerlEcho: now, via, popen()
*/