Execlp无法正常工作

Question

The user must type the command and the program should execute it. I am using fork() and execlp() but is not working. I am printing comando and ruta to see if they are good. I dont know how to make it different in order to make it work.

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include<string.h>

int main(){
char comando[10];
char ruta[40];
printf("Type a command: ");
fgets(comando,10,stdin);

pid_t pid;
pid = fork();

if (pid < 0){
    perror("Error");
    return -1;
}
else if (pid == 0){ 
strcpy (ruta,"/bin/");
strcat (ruta,comando);
printf("%s",ruta);
printf("%s",comando);
execlp(ruta, comando,NULL);   
}
else{
    wait(NULL); }

return 0;
}

Answer 1

execlp is not executung command because of fgets() , in above fgets() copies new line at the end of comando . see the manual page of fgets()

Remove the new line as

fgets(comando,sizeof(comando),stdin); 
comando[strlen(comando)-1] ='\0'; /* replacing '\n' with '\0' */

OR you can use strcspn() below as suggested by @Jonathan Leffler.

comando[strcspn(comando, "\n"))] = '\0';

Complete working code

int main(){
        char comando[10];
        char ruta[40];
        printf("Type a command: ");
        fgets(comando,sizeof(comando),stdin); 
        comando[strlen(comando)-1] ='\0';
        pid_t pid;
        pid = fork();
        if (pid < 0){
                perror("Error");
                return -1;
        }
        else if (pid == 0){ 
                strcpy (ruta,"/bin/");
                strcat (ruta,comando);  
                execlp(ruta, comando,NULL);
        }
        else{
                wait(NULL); 
        }
        return 0;
}

Answer 2

Not all executables are in /bin . The point of execlp and the other exec functions with p in the name is that they look for the requested program in $PATH for you.

To help debug this kind of thing in the future, or if this doesn't work, you should check errno after every system call (which is what perror does after you fork ). When exec*() -family functions work, they don't return; when they fail, they set errno appropriately before returning.