File Descriptor Help

Thread Tools Search this Thread
# 1  
Question File Descriptor Help

What is a file descriptor in Unix??

How to find a file descriptor of a file in Unix??

Does it have anything to do with the Inode numbers??
# 2  

u c an use stat structure and find it
# 3  
Mr Arun Thanks for ur reply.

But i dint get it still.

Where is this stat structure located. Is it a command.
If it is it does n't run in SCO unix.

if it is a file where is it located.
# 4  
If you are familiar with UNIX I/O redirection, syntax similar to the following should not be new to you:
command > file 2>&1
When command runs it sends "normal" output to file, and any error messages generated by command are also written to file. "2>&1" handles the latter.

The 2 and 1 are file descriptors. So what's a file descriptor?

When a UNIX program wants to use a file, it must first open that file. When it does so, UNIX will associate a number with the file. This number, which is used by the program when reading from and writing to the file, is the file descriptor.

A typical UNIX program will open three files when it starts. These files are:

- standard input (also known as stdin)
- standard output (also known as stdout)
- standard error (also known as stderr)

Standard input has a file descriptor of 0, standard output uses 1, and the number 2 is used by standard error.

Previous Thread | Next Thread
Thread Tools Search this Thread
Search this Thread:
Advanced Search

Test Your Knowledge in Computers #827
Difficulty: Medium
Douglas Crockwell first specified and popularized the JSON format.
True or False?

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

redirecting with file descriptor

hello, Someone can help me with redirectors? I am writing this script in bash enviroment on Fedora: exec 4<> /dev/tcp/ #open socket in input/output strings<&4 >file.txt & I send file descriptor 4 to string command to purge data stream from special char while come from... (3 Replies)
Discussion started by: rattoeur
3 Replies

2. Shell Programming and Scripting

Variable File Descriptor

Greetings. I am happily using constructs like the following; I have set -x to show fine distinctions. $ exec 4> afile + exec + 4> afile $ print -u4 This is the first line in afileAs you can see from the -x expansion, the shell performed the exec command and redirected file descriptor to... (4 Replies)
Discussion started by: rpaskudniak
4 Replies

3. Shell Programming and Scripting

Help with File Descriptor in a While loop

Hi, I am trying to read a file line-by-line in a while loop, and perform some tasks which involves non-interactive SSH to a remote server. The code looks something like this -- #!/usr/bin/ksh export myFile=/path/to/my/file.load while read line do do something ## Adding the SSH... (2 Replies)
Discussion started by: Subu1987
2 Replies

4. Shell Programming and Scripting

file descriptor count

I am trying to write a script which will only show me the file descriptor count for a process/pid. My script will return me the count only not the whole output. For example, I would like my script to return the output 23 this case, not the whole output. Can anybody please help me how do I get... (11 Replies)
Discussion started by: mohullah
11 Replies

5. UNIX for Dummies Questions & Answers

File Descriptor

Hi What the below path contains? /proc/<pid>/fd (1 Reply)
Discussion started by: siba.s.nayak
1 Replies

6. Shell Programming and Scripting

File Descriptor

Hello All, Im opening a file desciptor in perl and sending data using print CMD "$xyz". is there a limit to the length of the string that I can give to this CMD at a time. (3 Replies)
Discussion started by: rimser9
3 Replies

7. UNIX for Advanced & Expert Users

File Descriptor Table

Im working on writing a small operating system. I am currently working on implementing dup, dup2, pipe, and close and I need to implement some type of file descriptor table in my PCB. I was wondering if there is anyone who is familiar with linux/unix implementation of these tables who could... (6 Replies)
Discussion started by: Ashaman0
6 Replies

8. Programming

File descriptor constant

I have a requirement to close all the file descriptors from 3 to 1024 for a particular application. Right now, this is how I do it .. for ( int i = 3 ; i <= 1024; ++i ) close(i); The change I am looking at is, I want to do away with the number 1024 and replace it with a constant which... (4 Replies)
Discussion started by: vino
4 Replies

9. UNIX for Dummies Questions & Answers

file activity (open/closed) file descriptor info using KORN shell scripting

I am trying to find a way to check the current status of a file. Such as some cron job processes are dependent on the completion of others. if a file is currently being accessed / modified or simply open state I will wait until it is done being processed before attempting the next process on that... (3 Replies)
Discussion started by: Gary Dunn
3 Replies

10. UNIX for Dummies Questions & Answers

bad file descriptor?

Ok, I'm sure this is a total newbie question, but I think I'm in the right place, no? I'm trying to call a perl module from a cgi script - Mail::Sendmail - and my web host installed the module in a directory that doesn't seem to be accessible, at least not the way I'm trying. But I thought you... (1 Reply)
Discussion started by: ftb
1 Replies

Featured Tech Videos