if making a function popen using pipes/forks, then when calling that function giving "r" and the string, that means that the result of the string will go to the write end of the pipe, and a pointer to the read end of the pipe will be returned?
Also if given "w" instead of "r", then where does the result of the string go? I think that its supposed to return a pointer to the write end of the pipe... But I don't understand where the string output goes...
If you open it with "r", you're given the read-end of a pipe connected to its stdout.
if you open it with "w", you're given the write-end of a pipe connected to its stdin. I think the output is discarded (but aren't 100% sure -- it may go to stdout). Stuff written to stdout isn't a 'string' by the way -- string means something specific and that's not it.
Note that this is not quite the usual file-handle. You have to call pclose() on it, not fclose(), and nonstandard operations on it like fileno() may not do quite what you expect.
You don't have to write your own popen(), stdio already has one.
Have you actually tried this code? It'll crash, because
That doesn't make a FILE pointer, just an integer pointer, since fd isn't a FILE. You convert a file number into a FILE * with a command like fdopen(fd, "r");
You also forgot to close the end of the pipe you're not using again.
This doesn't work either:
You don't compare strings that way.
...and you have no way to wait for the process on close now, because you didn't store the PID anywhere. stdio popen() can do that and remember, but you can't just from a FILE *.
Honestly I think some review of the C language would do you good before you try to tackle multiprocessing.
Hello all,
I am reading a huge zip file in POPEN process and then writting that to a normal file which of 2GB. Now the process is failing when I looked for the cause someother process comming in after I read my file and it is deleting the zip. But in theory the popen command should read the... (5 Replies)
in man system it talks about SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.
Does this signal stuff also happen in popen command?
(even though man popen says nothing about signals)
also if I am not using wait(&status) and I am using waitpid(pid, NULL, 0)
how would... (1 Reply)
hi,
i am trying to use popen to run a grep process and check if the pattern exists in the file that i am searching in. i am getting segmentation fault when i try to execute the following code
char *cd;
char flag;
char hdr_flpsp;
char hdr_flpsp2;
FILE *fp;
printf ("program starts");... (1 Reply)
Hi
I am trying to use popen function with wrtie option to give inputs to ftp command.
#include "stdio.h"
int main(int argv ,char *argc)
{
int size=0;
char *buf;
FILE *fp;
fp = popen("ftp","w");
while(getline(&buf,&size,stdin) != -1)
write(fp,buf);... (0 Replies)
Hi!
I'm trying to write a c program. The child process must transmit to the parent a file name and the parent must count the lines from the file and return te result to the child. Here is what i've done. It doesn't stop running, I guess. I'm sorry if it's an ugly code, i'm new at this stuff,... (2 Replies)
Hello I'm writing a web server in python(obelisk-http.sourceforge.net)
and I'm having a greeat problem with POST method it like that
When someone make a POST request to the server it must open the executable(perl/python/.exe/elf) and send to the STANDART in (stdin) the request and get the... (2 Replies)
hi,
how to work with a background process without a controlling terminal to make use of popen or system call ?
when ever i use popen or system function call in foreground process, there is no problem with respect to that .. but when the same program is run as a background process without a... (7 Replies)
Hi there,
I'm facing a problem running the tar command with the popen function.
FILE* fp = popen("tar czf - textfile","r")
// output
this program should give the output to the stdout. I don't know if it is possible and which function like fprint() etc. should I use.
I suppose that I... (4 Replies)
hai friends
I have written a tcp chat server in c.. I have designed a cgi program in c to control it... When i try to start the server from the cgi program, it is not starting. Why is that ? I have even tried giving the root ownership for all the programs.. Still its not.
I have used the... (1 Reply)
Hi
The following is my program to test popen()
routine. The purpose is to print some contents
of the corrent directory.
But in fact, the output is only one character
'a', which I believe is the first char of the file
"a.out".
So, can anybody tell me what is wrong about
this program?... (2 Replies)