The popen() function shall execute the command specified by the string command. It shall create a pipe between the calling program and the executed command, and shall return a pointer to a stream that can be used to either read from or write to the pipe.
EXAMPLES
Using popen() to Obtain a List of Files from the ls Utility
The following example demonstrates the use of popen() and pclose() to execute the command ls * in order to obtain a list of files in the current directory:
#include <stdio.h>
...
FILE *fp;
int status;
char path[PATH_MAX];
fp = popen("ls *", "r");
if (fp == NULL)
/* Handle error */;
while (fgets(path, PATH_MAX, fp) != NULL)
printf("%s", path);
status = pclose(fp);
if (status == -1) {
/* Error reported by pclose() */
...
} else {
/* Use macros described under wait() to inspect `status' in order
to determine success/failure of command executed by popen() */
...
}
| execute the command **grep ‘processor’ /proc/cpuinfo | sort -u | wc -l** |
int get_processor_num()
{
FILE *fstream=NULL;
char buff[1024];
memset(buff,0,sizeof(buff));
if(NULL==(fstream=popen("grep 'processor' /proc/cpuinfo | sort -u | wc -l","r")))
{
return -1;
}
fgets(buff, sizeof(buff), fstream);
printf("%s", buff);
pclose(fstream);
return 0;
}
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