Passing parameters from C code to bash script

[clickit]

Here is my test code because my other code is too long:

#!/bin/bash
rdstr=`./rdchn`
let "rdval = $rdstr"
echo -e "rdval=$rdval"
exit
and this is the C code it calls:
val = val + val + ... ;  //This line does work used elsewhere
printf("From RDCHN>> %d\n", val);
sprintf(str, "%s", val);                                 //converts to string
printf("From rdchn>> %s\n", str);

there is a printf cmd to output str with a \n following it for the benefit of the rdstr=`./rdchn` bash script, and I am aware that the other print statements are now in the way of it.
I get no print to stdout on screen from the C code.
Does bash somehow block or mask it?

I get print from bash. I get this error in the non-test bash script like: let "rdval = $rdstr"
syntax error: operand expected (error token is " ")
The let command prints rdval= but I presume this is due to the printf test statements getting in the way.
I am getting no compile errors. Why does the C code not print the values specified?

[drl]

Hi.

I made several changes in your posting, including making a complete script and c program, and using CODE tags for easier reading:

#!/usr/bin/env bash

# @(#) s1	Demonstrate capture of results into shell variable.

# Utility functions: print-as-echo, print-line-with-visual-space, debug.
pe() { for i;do printf "%s" "$i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
db() { ( printf " db, ";for i;do printf "%s" "$i";done; printf "\n" ) >&2 ; }
db() { : ; }
C=$HOME/bin/context && [ -f $C ] && . $C gcc

FILE=${1-c1.c}
pl " Amended c code:"
cat $FILE

pl " Compile and identify c code:"
rm -f c1
gcc -o c1 $FILE
file c1

pl " Results from amended script and code:"
# rdstr=`./rdchn`
rdstr=`./c1`
# let "rdval = $rdstr"
rdval=$rdstr
echo -e "rdval=$rdval"
rm -f c1

exit

producing:

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0.7 (lenny) 
GNU bash 3.2.39
gcc (Debian 4.3.2-1.1) 4.3.2

-----
 Amended c code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define VERSION  "1.0"
#define PROGRAM  "main"

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

  printf (" Hello, world from c: %s, %s.\n", PROGRAM, VERSION);

  int val = 2;
  char *str;
  str = malloc (80);
  val = val + val;		//This line does work used elsewhere
  printf ("From RDCHN>> %d\n", val);
  // sprintf(str, "%s", val); //converts to string
  sprintf (str, "%d", val);	//converts to string
  printf ("From rdchn>> %s\n", str);

}

-----
 Compile and identify c code:
c1: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.8, not stripped

-----
 Results from amended script and code:
rdval= Hello, world from c: main, 1.0.
From RDCHN>> 4
From rdchn>> 4

See man pages and google for details ... cheers, drl

[clickit]

TNX drl. Turns out I needed to fix was include string.h and fix my sprintf. Learned your neat trick as well. Yeh yeh on CODE tags, can never remember how to do those.