C 程序在 bash 脚本中

Question

I am trying to run C program inside bash, my C program is using the gps device and calculating the distance based on latitude and longitude values. The problem is when i run this C program through bash to get distance, i am not able to redirect its output to any file or variable. i tried this: output=$(./run) but it is not working. to run C code inside bash i am using the following code:

#!/bin/bash

echo 'clear'

echo enter file name

read FILE

gcc -o a.out $FILE -lm 
output=$(./a.out) 
echo $output

when i do not redirect it shows value:

#!/bin/bash
echo `clear`
echo enter file name
read FILE
gcc -o a.out $FILE -lm 

./a.out

[gps values ][1]

Can any body help in this?

Answer 1

You don't include the requested debug log, but from your screenshot it looks like your program never exits. It just stays around and writes values forever. Therefore, the capture never reaches the end, so your echo statement never executes.

You should modify your program or invocation so that it will at some point exit.

If you can't modify the program, you can capture eg only the first ten lines using one of:

# More canonical way
output=$(./a.out | head -n 10)

# More resilient way, if the program is especially poorly written
output=$( head -n 10 <(./a.out) ) 

Answer 2

Thank you every one for the comments It is working now

#!/bin/bash

echo `clear`
echo enter file name
read FILE
gcc -o a.out $FILE -lm 

stdbuf -oL ./a.out |
  while IFS= read -r line
  do
    echo "Data: $line"
  done

by using the above code

Answer 3

Use -o flag in gcc to create the binary first.

I'll give you an example using "Hello World" code:

~]# cat hw.c
#include <stdio.h>

int main(){
        printf("Hello World");
        return 0;
}

The bash script:

~]# cat hw.sh
gcc -o hw hw.c
./hw

Then run:

~]# bash hw.sh
Hello World