Login or Register to Ask a Question and Join Our Community


UNIX for Dummies Questions & Answers

File Descriptor Help

 
Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers File Descriptor Help
# 1  
Old 10-14-2004
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  
Old 10-14-2004
file
Rathore
u c an use stat structure and find it
arun
# 3  
Old 10-14-2004
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  
Old 10-14-2004
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.
 
Login or Register to Ask a Question

Previous Thread | Next Thread

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/10.10.11.30/5000 #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. Shell Programming and Scripting

file descriptor KSH

Hello, How can i use file descriptor in a script to read 2 files at the same time and extract line 200 from file 1 and line 500 from file 2. Thanks. (6 Replies)
Discussion started by: LiorAmitai
6 Replies

6. 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

7. 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

8. Shell Programming and Scripting

Passing a file descriptor

I am trying to right a function which uses a file descriptor to write to a log file. The problem is that the on the print statement the file descriptor is called bad. Now when I first open the file and print to it in the f_open function by passing the descriptor to f_print_log all works well,... (6 Replies)
Discussion started by: robotball
6 Replies

9. 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

10. 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
Login or Register to Ask a Question