need help with execl command

Shell Programming and Scripting
1

I want to make simultanous sh commands in an exec command

for example I want to counts the lines in a file

wc -l my file.txt | awk -F" " '{print $1}'` works fine in sh but I want to implement it in a c code

the first part works like this

execl("/usr/bin/wc", "wc", "-l", "myfile.txt", (char *)0);

for the second part it will be sth like this I think
execl("/bin/awk", "awk", "-F", "'{print $1}'", (char *)0);

I want to implement this two command together like in the sh commands

I want to bound to first exec command's output to second exec command's output like as what the " | " operatoretor does in shell.

and also I want to assign final output to a variable in c

I know this is a little bit long but It will be greatfull if anyone can help me, Thanks soo much..

2

Since it bit too late that someone is answering I would just like to ask are u still in search of ur answer if yes I'm listing code for what u desired below:

/* listing - cpipe.c*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#define CLOSEALL()	close(pipefd[0]),close(pipefd[1])

int main(int argc,char *argv[]){
		int pipefd[2],fd;
		pid_t pid1,pid2;
		int result;
		
		if (argc < 2){
			printf("Argument Missing\nUsage: ./cpipe filename\n");
			exit(1);
		}

		if (pipe(pipefd) < 0){
			perror("pipe:");
			exit(1);
		}
		
		pid1 = fork();
		
		if(pid1==-1){
				perror("fork");
				exit(1);
			   }

	        else if(pid1==0){

				pid2 = fork();
				if(pid2 == -1){
					perror("fork");
					exit(1);
				}
				else if(pid2 == 0){
				dup2(pipefd[1],STDOUT_FILENO);
				CLOSEALL();
				if(execlp("/usr/bin/wc","wc","-l",argv[1],0)< 0){
					perror("execlp");
					exit(1);
				}
				}
		
				else{
				dup2(pipefd[0],STDIN_FILENO);
				if((fd = open("temp",O_RDWR|O_CREAT|O_TRUNC,0666))==-1){
				perror("open");
				exit(1);
				}
				dup2(fd,STDOUT_FILENO);
				CLOSEALL();
				close(fd);
				if(execlp("/usr/bin/awk","awk","-F"," ","{print $1}",0) < 0){
				perror("execlp");
				exit(1);
				}
		    	}
			}
		
		else{
			CLOSEALL();
			waitpid(pid1,NULL,0);
			FILE *fp = fopen("temp","r");
			fscanf(fp,"%d",&result);
			fclose(fp);
			//unlink("temp");
			printf("And the result is :: %d\n",result);
		    }

		return 0;
	 }

As the code is self-explanatory only few thing demand some clarification. The basic idea is that we use execute the different commands in different processes and output of one is fed to another using pipes and redirection (using pipe() and dup2(). U may use freopen() for redirection which is nothing but just the combination of these two only). Next the final output is redirected to a file (otherwise it will be displayed on terminal) which can then be read easily into some variable (here 'result'. Since I don't know how do u want to use this 'result' I've just displayed it back but u can do as u like).
Also u may want to delete the file that stores ur output temporarily (here 'temp'). U can call unlink() to do so (Though I've commented it out for this would require file to be created every time u run the prog. an unneccessary operation but if its necessary to keep data secret or for any other reason u may either name the file '.temp' to hide it or uncomment the unlink()).
If any more elaboration is required let me know. I'll try to dispell ur doubts. U can also get some refernces for it in Unix System Programming by Terrance Chan or Advanced Unix Programming by Stevens