Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

Handling stdout

Posted on 2000-03-31
11
Medium Priority
?
427 Views
Last Modified: 2010-04-22
In a C program, I want to close the file stream associated with stdout [ something like fclose(stdout);] and open it again. Who can tell me how can I do this?
I use Linux and gcc.
Thanks
0
Comment
Question by:mateif
11 Comments
 
LVL 10

Expert Comment

by:rbr
ID: 2672559
man freopen
0
 

Author Comment

by:mateif
ID: 2672647
What I want to do is to reopen the stream and associate it with stdout again. Using freopen would require a first argument ( char *path) and I don't know which would that be. I tried NULL and it didn't work out.
0
 
LVL 10

Expert Comment

by:rbr
ID: 2672656
So why want you to close it. If you just want to flush buffers use fflush (stdin);
0
NFR key for Veeam Agent for Linux

Veeam is happy to provide a free NFR license for one year.  It allows for the non‑production use and valid for five workstations and two servers. Veeam Agent for Linux is a simple backup tool for your Linux installations, both on‑premises and in the public cloud.

 
LVL 10

Expert Comment

by:rbr
ID: 2672658
Sorry use
fflush (stdout);
0
 

Author Comment

by:mateif
ID: 2672757
What I want is to display two pages with a cgi, without stopping the cgi. The two pages are constructed by the cgi, and i don't want to save them on the hard-disk. So I saw that if i close stdout it displays the first page, so i need to reopen it to display the second. I tried to input EOF in stdout, but it didn't work.
0
 
LVL 40

Expert Comment

by:jlevie
ID: 2675943
I think that rbr's suggestion is what you need. Try flushing the buffers and it should push the data out.
0
 

Author Comment

by:mateif
ID: 2679032
Flushing the buffer has no effect. I tried.
0
 
LVL 10

Expert Comment

by:rbr
ID: 2679301
Can you post your code pls. I'm not sure what your problem is.
0
 
LVL 2

Expert Comment

by:fremsley
ID: 2679683
have you tried to write a formfeed ('\f') or an Unix EOF ('\004')? note: the constant EOF is not a valid character to write to stream.
0
 
LVL 3

Expert Comment

by:alien_life_form
ID: 2680250
Greetings.

If I understand correctly what you want to do, the answer is: 'You cannot, because the CGI protocol prevents it'.

You cannot output two CGI pages during the same transaction, because the web server will just leave and close the client transaction after you're done with the first one. When your CGI starts up, your stdout is connected - through a socket - to the browser. After you're done with the transaction, the browser renders the page and *goes away* - it does not come back looking for seconds.

If persistent/multistep  connections are what you want, you need to go with different techniques (Cookies, hidden fields, php, and/or more). Fiddling with file handles won't buy you anything (regretfully).

Cheers,
    alf
0
 
LVL 1

Accepted Solution

by:
zx9r earned 300 total points
ID: 2735128
do the following steps:

1. copy the file descriptor of the stdout :
       int fd;
       fd = dup(stdout);

2. close stdout
      close(stdout);

3. do the job
      here is important to not open any file or if you open any, make sure that       you close it before continuing with the next step

4. to restaure stdout you only have to do
      dup2(fd, stdout);
0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

The purpose of this article is to fix the unknown display problem in Linux Mint operating system. After installing the OS if you see Display monitor is not recognized then we can install "MESA" utilities to fix this problem or we can install additio…
The purpose of this article is to demonstrate how we can upgrade Python from version 2.7.6 to Python 2.7.10 on the Linux Mint operating system. I am using an Oracle Virtual Box where I have installed Linux Mint operating system version 17.2. Once yo…
This Micro Tutorial will teach you how to add a cinematic look to any film or video out there. There are very few simple steps that you will follow to do so. This will be demonstrated using Adobe Premiere Pro CS6.
Whether it be Exchange Server Crash Issues, Dirty Shutdown Errors or Failed to mount error, Stellar Phoenix Mailbox Exchange Recovery has always got your back. With the help of its easy to understand user interface and 3 simple steps recovery proced…
Suggested Courses

876 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question