01-10-2009
I fail to see what you gain by doing this as a general idea.
In theory close the descriptors, then open them again directed somewhere else.
As a special case:
When you write a daemon all three of these descriptors are closed and then often reopened and directed to /dev/null. This means because the process runs "in the dark" it cannot directly write or read any of the standard descriptors. This prevents signals like SIGTTOU being sent to the process if it inadvertantly tries to write to stdout while running in detached mode.
10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
This is likely to be a dumb one.
How can I use sed to substitute string occurances having it read from an input file and write to this very same file ?
I have a file with lots of occurances of '2006', I want to change it to '2007', but I'd like these changes to be saved on the input file.
... (5 Replies)
Discussion started by: 435 Gavea
5 Replies
2. Shell Programming and Scripting
I have tried to show the file name whose size is greater than 200 byte in current directory.
Please help me.
ls -l | tr -s " " " " | cut -f 5,9 -d " " >out.txt
#set -a x `cat out.txt`
i=0
`cat out.txt` | while
do
read x
echo $x
#re=200
j=0
if }" < "200" ]
then
echo $j
j=`expr $j... (2 Replies)
Discussion started by: rinku
2 Replies
3. Shell Programming and Scripting
Is there any way to write to a text file with scripting? I need to write to a text file two lines of text for the amount of files in the current directory. (9 Replies)
Discussion started by: Fred Goldman
9 Replies
4. IP Networking
Hi,
We have smb client running on two of the linux boxes and smb server on another linux system. During a backup operation which uses smb, read of a file was allowed while write to the same file was going on.Also simultaneous writes to the same file were allowed.Following are the settings in the... (1 Reply)
Discussion started by: swatidas11
1 Replies
5. Shell Programming and Scripting
hi
i am quite new to shell scripting and need help in reading and writing in xml file
i have an xml file with format:
<main>
<store>
<name>ABC</name>
<flag>0</flag>
<size>123<size>
</store>
<store>
<name>DEF</name>
... (2 Replies)
Discussion started by: kichu
2 Replies
6. UNIX for Dummies Questions & Answers
hello world, i was looking for exemples for writing ans reading in / from a file, more exactly a text file; and how i'm only at very beagining, if anyone have some exemples very simple, very 'classic' , -with explications- and not hard to undersand . i was wondering that some of you are theacher... (6 Replies)
Discussion started by: unumai
6 Replies
7. Shell Programming and Scripting
I have got a file in following format:
AAAAAAA
BBBBBBBB
CCCCCCC
DDDDDDD
I am trying to read this file and out put it in following format:
AAAAAAA,BBBBBBB,CCCCCCC,DDDDDD
Preferred method is shell or Perl.
Any help appreciated. (11 Replies)
Discussion started by: Araoki
11 Replies
8. Shell Programming and Scripting
Hello Guys, How all are doing?
I have an issue in Unix and want help from all of you
I have a file in UNIX which it read by line by line , If at the end of line '0' is written the it should fetch that line into another file and change '0' to '1'
and If at the end of line '1' is written then it... (10 Replies)
Discussion started by: adisky123
10 Replies
9. Shell Programming and Scripting
Hi,
I am trying to do a write operation followed by a read operation on the same file through Perl, expecting the output produced by read to contain the new lines added, as follows:
#! /usr/bin/perl -w
open FH, "+< testfile" or die "$@";
print FH "New content added\n";
while (my $line =... (1 Reply)
Discussion started by: royalibrahim
1 Replies
10. Shell Programming and Scripting
What I would like to do is read each line in the atdinfile:
A sample atdinfile would look like this:
651
652
653
654
655
656
657
658
659
660
661
664
665
666
667
668 (5 Replies)
Discussion started by: woodson2
5 Replies
CLOSE(2) BSD System Calls Manual CLOSE(2)
NAME
close -- delete a descriptor
SYNOPSIS
#include <unistd.h>
int
close(int fildes);
DESCRIPTION
The close() call deletes a descriptor from the per-process object reference table. If this is the last reference to the underlying object,
the object will be deactivated. For example, on the last close of a file the current seek pointer associated with the file is lost; on the
last close of a socket(2) associated naming information and queued data are discarded; on the last close of a file holding an advisory lock
the lock is released (see further flock(2)).
When a process exits, all associated file descriptors are freed, but since there is a limit on active descriptors per processes, the close()
function call is useful when a large quantity of file descriptors are being handled.
When a process forks (see fork(2)), all descriptors for the new child process reference the same objects as they did in the parent before the
fork. If a new process is then to be run using execve(2), the process would normally inherit these descriptors. Most of the descriptors can
be rearranged with dup2(2) or deleted with close() before the execve is attempted, but if some of these descriptors will still be needed if
the execve fails, it is necessary to arrange for them to be closed if the execve succeeds. For this reason, the call ``fcntl(d, F_SETFD,
1)'' is provided, which arranges that a descriptor will be closed after a successful execve; the call ``fcntl(d, F_SETFD, 0)'' restores the
default, which is to not close the descriptor.
RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and the global integer variable errno is set to
indicate the error.
ERRORS
The close() system call will fail if:
[EBADF] fildes is not a valid, active file descriptor.
[EINTR] Its execution was interrupted by a signal.
[EIO] A previously-uncommitted write(2) encountered an input/output error.
SEE ALSO
accept(2), execve(2), fcntl(2), flock(2), open(2), pipe(2), socket(2), socketpair(2)
STANDARDS
close() conforms to IEEE Std 1003.1-1988 (``POSIX.1'').
4th Berkeley Distribution April 19, 1994 4th Berkeley Distribution