linux下popen函数用法代码

// linux下popen函数用法代码：zread.c，摘自gzip例子
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Trivial example of reading a gzip'ed file or gzip'ed standard input
* using stdio functions fread(), getc(), etc... fseek() is not supported.
* Modify according to your needs. You can easily construct the symmetric
* zwrite program.
*
* Usage: zread [file[.gz]]
* This programs assumes that gzip is somewhere in your path.
*/
int main(argc, argv)
int argc;
char **argv;
{
FILE *infile;
char cmd[256];
char buf[BUFSIZ];
int n;

if (argc < 1 || argc > 2) {
fprintf(stderr, "usage: %s [file[.gz]]\n", argv[0]);
exit(EXIT_FAILURE);
}
strcpy(cmd, "gzip -dc ");  /* use "gzip -c" for zwrite */
if (argc == 2) {
strncat(cmd, argv[1], sizeof(cmd)-strlen(cmd));
}
infile = popen(cmd, "r");  /* use "w" for zwrite */
if (infile == NULL) {
fprintf(stderr, "%s: popen('%s', 'r') failed\n", argv[0], cmd);
exit(EXIT_FAILURE);
}
/* Read one byte using getc: */
n = getc(infile);
if (n == EOF) {
pclose(infile);
exit(EXIT_SUCCESS);
}
putchar(n);

/* Read the rest using fread: */
for (;;) {
n = fread(buf, 1, BUFSIZ, infile);
if (n <= 0) break;
fwrite(buf, 1, n, stdout);
}
if (pclose(infile) != 0) {
fprintf(stderr, "%s: pclose failed\n", argv[0]);
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
return 0; /* just to make compiler happy */
}