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

 

[CBFalconer]

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.

 

[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

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

 

[Keith Thompson]

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.