c - Child Fork Process using fork() and pipe() -

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i have create pipe creates 2 child processes fork(). child 1 redirects stdout write end of pipe , executes execlp() "ls -al" command. child 2 redirects input stdin read end of pipe, executes "sort -n -k 5" command. after creating both children, parent process waits them terminate before can exit. when run code, gives following output:

pipes pipes.c pipes.c~

the parent program same thing shell runs command "ls -al | sort -r -n -k 5". when command line, following:

-rwxrwxr-x 1 username username 8910 may 28 21:52 pipes drwxrwxr-x 3 username username 4096 may 28 13:52 .. drwxrwxr-x 2 username username 4096 may 28 21:52 . -rwxrwxr-x 1 username username 1186 may 28 21:52 pipes.c -rwxrwxr-x 1 username username 1186 may 28 19:48 pipes.c~

is there im not doing correctly in code output? tips?

my code:

#include <stdio.h> #include <string.h>   // strlen #include <stdlib.h>   // exit #include <sys/types.h> #include <sys/wait.h> #include <unistd.h>   int main() {     int pipes[2];     pid_t child1, child2;   //pipe          int p = pipe(pipes);         if (p<0){   //pipe fails              fprintf(stderr, "pipe fail");              exit(2);         }  //child2 process               child2 = fork(); //creating child2         if(child2 < 0){//fork fail               fprintf(stderr, "child2 fork failed\n\n");               exit(3);         }else if(child2 > 0){ //parent  //child1 process               child1 = fork(); //creating child1         if(child1 <0){//fork fail               fprintf(stderr, "child1 fork failed\n\n");               exit(4);         }else if(child1 ==0){//child1 p               dup2(pipes[1], 1);               close(pipes[0]);               execlp("ls","-al",null);         }               wait(null);//parent waits         }          else if(child2 ==0){ //child2               dup2(pipes[0],0);               close(pipes[1]);                execlp("sort", "-r", "-n", "-k" , "5", null);         }      return 0; }

exec , friends expect provide arguments new program's argv vector. remember convention, argv[0] name of program, , command-line arguments begin @ argv[1].

but not providing argv[0] argument, example ls thinks called through symbolic link named -al , not given arguments.

the right way is

execlp("ls", "ls", "-al", null);

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