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C take input from Bash Script

Posts: 42
in Software Development

Hi,

I make a simple c file which takes input from user and then display it. I am trying to make a bash script in which i predefined those input and then run the c program inside bash and the c program takes the input which i have defined (i.e. user don't need to enter the input)

Here is the code.

#include<stdio.h>
void main()
{
char ch;
int num;
printf("Enter a single character:\n");
scanf("%c", &ch);
printf("Enter any number:\n");
scanf("%d", &num);

printf("You type charachter %c\n", ch);
printf("You type number %d\n", num);
}

And here is the bash file

#!/bin/bash

ch=s

num=2

./test < $ch $num


When i run the bash script it don't take the input values of ch and num. then i find on Google to use | so i tried ./test | $ch $num but didn't work

Please help me.

Thank you

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Comments

  • Posts: 501
    ./test << EOF
    $ch
    $num
    EOF
  • Posts: 1
    What you did in your bash script is correct, but you might as well write "./test s 2"
    In fact, when bash encounter '$varname', it replace it first with the value of the variable varname, before the function call, so the line is converted to "./test s 2" before bash calls the c file, which is the moment when ./test s 2 is converted to an array with tree pointer to "./test\0", "s\0" and "2\0".
    This array can be acceded by defining main like "int main (int argc, char ** argv)"
    (argc and argv are named by convention, but there types ca not be changed)
    argv is the array bash where bash putted the words of the line that called the c file.
    You can then access to 's' and '2' with argv[1][0] and argv[2][0].
    The next thing you might want to do is convert 2 in an integer, so you might find this (http://stackoverflow.com...convert-string-to-integer...) usefull.
  • Posts: 1
    edited August 2015
    usmangt wrote:
    And here is the bash file 
    1. #!/bin/bash
    2.  
    3. ch=s
    4.  
    5. num=2
    6.  
    7. ./test < $ch $num

    When i run the bash script it don't take the input values of ch and num. then i find on Google to use | so i tried ./test | $ch $num but didn't work

    Please help me.


    Thank you

    You are treating $ch like it is a file and you are using the pipe symbol backwards.

    Try: 
    1. echo $ch $num | ./test

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