Problems implementing popen()

[Rob Hoelz]

Hello everyone,

I've been trying to roll my own popen(), but I've run into problems.
Would anyone care to look at my code and tell me what I'm doing wrong?

Here's my code:

#include <errno.h>
#include <stdio.h>
#include <unistd.h>

FILE *mypopen(const char *file, const char **argv)
{
int pid;
int filedes[2];

if(pipe(filedes))
return NULL;

pid = fork();
if(pid == -1) {
return NULL;
} else if(! pid) {
close(filedes[1]);
dup2(filedes[0], fileno(stdout));
execvp(file, argv);
} else {
close(filedes[0]);
return fdopen(filedes[1], "r");
}
}

int main(int argc, char **argv)
{
FILE *file;
const char *args[3] = {"hg", "status", NULL};
int inchar;

file = mypopen("hg", args);
if(! file) {
return 1;
} else {
inchar = fgetc(file);
while(inchar != EOF) {
fputc(inchar, stdout);
inchar = fgetc(file);
}
fclose(file);
}
return 0;
}

Thanks,
Rob Hoelz

[Rob Hoelz]

Rob Hoelz <ho***@wisc.eduwrote:

Hello everyone,

I've been trying to roll my own popen(), but I've run into problems.
Would anyone care to look at my code and tell me what I'm doing wrong?

Here's my code:

#include <errno.h>
#include <stdio.h>
#include <unistd.h>

FILE *mypopen(const char *file, const char **argv)
{
int pid;
int filedes[2];

if(pipe(filedes))
return NULL;

pid = fork();
if(pid == -1) {
return NULL;
} else if(! pid) {
close(filedes[1]);
dup2(filedes[0], fileno(stdout));
execvp(file, argv);
} else {
close(filedes[0]);
return fdopen(filedes[1], "r");
}
}

int main(int argc, char **argv)
{
FILE *file;
const char *args[3] = {"hg", "status", NULL};
int inchar;

file = mypopen("hg", args);
if(! file) {
return 1;
} else {
inchar = fgetc(file);
while(inchar != EOF) {
fputc(inchar, stdout);
inchar = fgetc(file);
}
fclose(file);
}
return 0;
}

Thanks,
Rob Hoelz

Nevermind...I need to learn to read man pages more closely...

[Keith Thompson]

Rob Hoelz <ho***@wisc.eduwrites:

I've been trying to roll my own popen(), but I've run into problems.
Would anyone care to look at my code and tell me what I'm doing wrong?

Here's my code:

#include <errno.h>
#include <stdio.h>
#include <unistd.h>

[snip]
pipe(), fork(), et al are not defined by the C standard.
Try comp.unix.programmer.

--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[CBFalconer]

Rob Hoelz wrote:

>
I've been trying to roll my own popen(), but I've run into problems.
Would anyone care to look at my code and tell me what I'm doing wrong?

Here's my code:

#include <errno.h>
#include <stdio.h>
#include <unistd.h>

FILE *mypopen(const char *file, const char **argv)
{
int pid;
int filedes[2];

if(pipe(filedes))
return NULL;

pid = fork();

Wrong newsgroup. So far unistd.h, pipe(), fork() etc. are all
unknown to standard C. Try comp.unix.programmer. My guess is that
you can't write portable system functions.

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net>

--
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