Тестовые примеры / ch8 / test_popen

		#include <stdio.h>

		#include <stdlib.h>

		#include <unistd.h>

		#include <sys/types.h>

		#include <sys/wait.h>

		#include <string.h>

		#include <limits.h>



		struct sh_rec 

		{

				pid_t	sh_pid;

				FILE*		stream;

		}					sh_info[OPEN_MAX];

		static	 int				num_sh;

	

		FILE* popen(const char* shell_cmd, const char* mode)

		{

				int 	fifo[2];

				if ((strcmp(mode,"r") && strcmp(mode,"w")) || pipe(fifo)==-1)

					return 0;

				switch (sh_info[num_sh].sh_pid=fork()) 

				{

					case -1:			perror("fork"); return 0;

					case 0	:		(*mode=='r')  	? 	dup2(fifo[1],STDOUT_FILENO) 						:												

										dup2(fifo[0],STDIN_FILENO);

								close(fifo[0]);

								close(fifo[1]);

								execl("/bin/sh", "sh", "-c", shell_cmd, 0);

								exit(5);

				}

				if (*mode=='r') 

				{

					close(fifo[1]); 

					return (sh_info[num_sh++].stream=fdopen(fifo[0],mode));

				} else 

				{

					close(fifo[0]);

					return (sh_info[num_sh++].stream=fdopen(fifo[1],mode));

				}

		}

		int pclose (FILE *fstream )

		{

				int 	i, status, rc=-1;

				for (i=0; i < num_sh; i++) 

					if (sh_info[i].stream==fstream) break;

				if (i == num_sh) return -1; 						/* invalid fstream value */

				fclose(fstream);

				if (waitpid(sh_info[i].sh_pid,&status,0)==sh_info[i].sh_pid ||

										WIFEXITED(status))

					rc = WEXITSTATUS(status);

				for (i++; i < num_sh; i++) sh_info[i-1] = sh_info[i];

				num_sh--;

				return rc;

		}

		int main (int argc, char* argv[])

		{

				char	buf[256], *mode= (argc>2) ? "w" : "r";

				FILE	*fptr;

	

				if (argc>1 && (fptr = popen(argv[1],mode)))

				{

					switch (*mode) 

					{

						case 'r':			while (fgets(buf,256,fptr)) fputs(buf,stdout);

									break;

						case 'w':			fprintf(fptr,"%s\n",argv[2]);

					}

					return pclose(fptr);

				}

				return 5;

		}