[英]C - pipe without using popen
我怎么能改變這個:
FILE *f;
char in_buffer[80];
f=popen("command","r");
fgets(in_buffer,sizeof(in_buffer),f)
不使用popen()
,而只使用pipe()
或其他指令?
這是我的簡單實現,其中的注釋解釋了正在做什么。
#include <unistd.h>
#include <stdio.h>
FILE *
my_popen (const char *cmd)
{
int fd[2];
int read_fd, write_fd;
int pid;
/* First, create a pipe and a pair of file descriptors for its both ends */
pipe(fd);
read_fd = fd[0];
write_fd = fd[1];
/* Now fork in order to create process from we'll read from */
pid = fork();
if (pid == 0) {
/* Child process */
/* Close "read" endpoint - child will only use write end */
close(read_fd);
/* Now "bind" fd 1 (standard output) to our "write" end of pipe */
dup2(write_fd,1);
/* Close original descriptor we got from pipe() */
close(write_fd);
/* Execute command via shell - this will replace current process */
execl("/bin/sh", "sh", "-c", cmd, NULL);
/* Don't let compiler be angry with us */
return NULL;
} else {
/* Parent */
/* Close "write" end, not needed in this process */
close(write_fd);
/* Parent process is simpler - just create FILE* from file descriptor,
for compatibility with popen() */
return fdopen(read_fd, "r");
}
}
int main ()
{
FILE *p = my_popen ("ls -l");
char buffer[1024];
while (fgets(buffer, 1024, p)) {
printf (" => %s", buffer);
}
fclose(p);
}
筆記:
popen
"r"
模式。 實現其他模式,即"w"
模式留給讀者練習。 pclose
實現留給讀者練習 - 見close
, waiptid
和fclose
。 如果你想看看真正的需求,你可以查看OSX , GNU glibc和OpenSolaris等來源。
希望這可以幫助!
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