c - linux execvp ; ls cannot access |, No such file or directory -

i trying code shell. shell doesn't execute command - ls -l | less. using execvp. code given below.

#include <stdio.h> #include <unistd.h> #include <string.h>  int main(){     int pid, status, num, len;     char str[1000], cwd[100];     char* word[100];      getcwd(cwd, sizeof(cwd));      while(1){         chdir(cwd);          printf("%s > ", cwd);          gets(str);          pid=vfork();          if(pid == 0){             num = 0;             word[num] = strtok (str, " ");              while (word[num] != null) {                 word[num] = strdup (word[num]);                 len = strlen (word[num]);                 if (strlen (word[num]) > 0)                     if (word[num][len-1] == '\n')                         word[num][len-1] = '\0';                 word[++num] = strtok (null, " ");             }              if(strcmp(word[0], "cd") == 0){                 chdir(word[1]);                 getcwd(cwd, sizeof(cwd));             }             else{                 execvp(word[0],word);             }              exit(0);         }         else{             wait(&status);         }     }      return 0; } 

ls -l | less shell command line consists of 2 processes connected pipe. execvp() call can spawn single process.

if want program, must invoke shell explicitly - either using system() call, or changing command line sh -c 'ls -l | less'. word array should this:

word[0] = "sh" word[1] = "-c" word[2] = "ls -l | less" word[3] = null 

[edit] alternatively, shell doing internally: spawn 2 processes , connect them pipe. involve using fork(), pipe(), dup2() , execve() calls. however, invoking shell less work, , since less interactive program anyway, don't need worry performance much: takes less 100 ms perceived instantaneous.