Popen functions called by C and Shell under Linux

Description:      This paper introduces the use and behavior mechanism of popen function, and gives practical examples to illustrate the use of popen function. The Popen function executes an external program using a FIFO pipeline, first let's look at the function prototype of Popen: #include <stdio.h>file *popen (const char *command, const char *type); int Pclose (FILE *stream);       popen determines the input/output direction of the command by Type R or W, and R and W are relative command pipes. R means the command is read in from the pipe, and W means that the command is output by the pipeline to its stdout,popen to return a file stream pointer to the FIFO pipeline. The pclose is used to close the pointer after the end of use. Let's look at an example:/********************************************************************************************* Name: popen.c**      this program was used to show the usage of Popen (). ***************************************** /#include <sys/types.h>  #include <unistd.h>   #include <stdlib.h>  #include <stdio.h>  #include <string.h>int main (void)  {     file   *stream;    file   *wstream;   char   buf[1024];         memset (buf, ' buf ', sizeof);//initialize BUF to avoid writing as garbled to file     stream = Popen ("Ls-l", "R"); The output of the "ls-l" command is read through the pipe ("r" parameter) to file* stream    Wstream = fopen ("Test_popen.txt", "w+"); Create a new writable file     fread (buf, sizeof (char), sizeof (BUF), stream); Read the data stream just file* stream into buf     fwrite (buf, 1, sizeof (BUF), wstream),//writes data from buf to file    * Wstream corresponds to the stream, also written to the file         Pclose (stream);     fclose (wstream);        return 0;}  [[email protected] src]# gcc popen.c [[email protected] src]#./a.out   [[email  Protected] src]# cat test_popen.txt  total 128-rwxr-xr-x 1 root root 5558 09-30 11:51 a.out-rwxr-xr-x 1 root root 542 09- 00:00 child_fork.c-rwxr-xr-x 1 root root 480 09-30 00:13 execve.c-rwxr-xr-x 1 root root 1811 09-29 21:33 FORK.C-RWXR-XR -X 1 root root 162 09-29 18:54 getpid.c-rwxr-xr-x 1 root root 1105 09-30 11:49 popen.c-rwxr-xr-x 1 root root 443 09-30 00:55 system.c-rwxr-xr-x 1 root root    0 09-30 11:51 test_popen.txt-rwxr-xr-x 1 root root 4094 09-30 11:39 te St.txt

Popen functions called by C and Shell under Linux