CODEWITHSUNDEEP
clinuxparameter-passingxterm
sherinkapotein
sherinkapotein

Reputation: 47

C-Passing arguments for execution of a program in new Xterm window

Problem statement:-

How to pass arguments to a program for execution in a new Xterm/Gnome window which will be calling through execlp.

A little elaborate explanation:-(oxymoron eh?)

Consider the following program which will take a string as argument and display it

//output.c
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[])
{
    if(argc<2)
        {
              printf("insufficient parameters\n");
              exit(1);
        }
    printf("%s",argv[1]);
    sleep(10);
    return 0;

}

And another program,client.cwhich, during the course of its execution is required to call output.c and make it display in a new xterm/gnome-terminal window.

//client.c
int main()
{
    char buf[25]="Test String";//as argument for program to be called
    int pid_child=fork();
    if(pid_child==-1)
            {
                printf("Fork Failed. Exiting");
                exit(1);
            }

    if(pid_child==0)
            {   
            execlp("/usr/bin/xterm","-e","./output",buf,NULL);
            }

    int status=0;
    while(wait(&status)!=-1);
}

The line of contention here is 

execlp("/usr/bin/xterm","-e","./output",buf,NULL); //With string `buf` as argument for `output`.

Result:-Does not run

Error -e: Explicit shell already was /~/cs60/directory/./output

-e: bad command line option "Test String"

execlp("/usr/bin/xterm","-e","./output",NULL);//Without passing variable `buf`

Result:- a) New Xterm window opens. b) output terminates with Insufficient parameters (as expected).

The manpage clearly states for Xterm:

-e program [ arguments ... ] 

            This option specifies the program (and its command  line  arguments) to be run in the xterm window.

It works perfectly fine when I run it from a terminal (as a script). But how can I achieve this through C.

Any help will be highly appreciated

Upvotes: 1

Views: 2730

Answers (1)

marty
marty

Reputation: 56

You need to understand how execlp() works.

You need to add a second argument to execlp with the command name ("xterm").

execlp("/usr/bin/xterm", "xterm", "-e", "./output", buf, NULL);

Also, your output program may want to do a fflush (so you see the output), and you should exit or otherwise take proper evasive action if execl() fails. Note that when the command name ("/usr/bin/xterm") contains any slashes, execlp() behaves the same as execl().

Upvotes: 3

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