External Programs

External programs are executables built outside but which can be launched from the Zsh command prompt.

If the command is neither built-in, nor specified with an absolute pathname, the shell will look in the \sys\bin on each drive in reverse alphabetical order ( y: , x: ,... to b: , a: and later z: ) and execute the first external program found.

To execute the external program directly give the following command at the command-prompt:

command <ext_pgm>

where ext_pgm is the name of the external program.

For example:

The program below reads input from Zsh and writes data to Zsh which can then be redirected back to the Telnet client.

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

int  main()
    {
    char userData[20]; char ch; int x=0;
    
    memset(userData,0,20);
    x=read(0,userData, 20);    
        
    while(strcmp(userData, "quit"))
        {
        write(1, userData, x);
        memset(userData,0,20);
        x=read(0,userData, 20);        
        }        
    return 0;                 
    }