By default stdin, stdout, and stderr are file descriptors opened during process creation.
If the file limit is 16, for example, then the process has 13 files descriptors to play with.
In shell scripts, redirection uses up file descriptors. Once the line "doing" the redirection has been completed the file descriptor is closed ie: ls * > myfile.txt. Redirecting blocks of code, like a loop, use up a file descriptor over many lines of code.
Cron jobs run without a tty, stdin is the script.
Hi,
I have written a daemon process, to perform certain operations in the background.
For this I have to close, the open file descriptors,
Does anybody know how to find out the number of open file descriptors ?
Thanks in Advance,
Sheetal (2 Replies)
Hello all,
A few questions on file descriptors ...
scenario : Sun Ultra 30 with Sun OS 5.5.1 , E250 with Solaris 2.6
In one of my servers, the file descriptor status from the soft limit and hard limits are 64 and 1024 respectively for root user.
Is the soft limit (64) represents the... (3 Replies)
i m trying to learn processes in unix and i've been reading this but i don't quite get it. its regarding file descriptors. : each is a part of file pointers, they point to another area. indexes into an Operating system maintained table called "file descriptor table". one table per process. may... (3 Replies)
I am in a Systems programming class this semester, and our current project is to write a program utilizing sockets and fork. For the project, I decided to make my own instant messaging program. I have the code completed, but I have a problem that keeps old clients from communicating with new... (3 Replies)
Need to close files which descriptor number are larger than 9 in ksh.
'exec 10>&-' fails with 'ksh: 10: not found'. How do you specify file descriptors which occupies two or more digits in ksh script?
Thanks,
Masaki (2 Replies)
Hi,
I speak and write english more or less, so I hope my asking be clear.
:)
In the company I am working, they are using control-m software to lunch
shell scripts.
So i put this command in all shell scripts:
export LOGFILE_tmp=$PRODUC_DATA/tmp/${SCRIPT}_${PAIS}_`date... (0 Replies)
What is the difference between a file descriptor and a semaphore?
My basic understanding is:
- a file descriptor is a small positive integer that the system uses instead of the file name to identify an open file or socket.
- a semaphore is a variable with a value that indicates the... (1 Reply)
Hi all,
I've been looking for the way to send stdout and stderr to different files. Well, actually I really knew how to make it, but I wanted to be sure.
I've found an instruction very interesting which I'm not able to understand:
taken from this site. It says it sends stdout to output.log,... (4 Replies)
Hi, I'm playing with KSH
I entered following command in terminal
{ echo "stdout" >&1; echo "stderr" >&2; } > out
And I get only stoud in a new file out.
My question is: Where did my stderr vanish ? (5 Replies)
Discussion started by: solaris_user
5 Replies
LEARN ABOUT BSD
close
CLOSE(2) System Calls Manual CLOSE(2)NAME
close - delete a descriptor
SYNOPSIS
close(d)
int d;
DESCRIPTION
The close call deletes a descriptor from the per-process object reference table. If this is the last reference to the underlying object,
then it 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)).
A close of all of a process's descriptors is automatic on exit, but since there is a limit on the number of active descriptors per process,
close is necessary for programs that deal with many descriptors.
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 descrip-
tors 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 VALUE
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
Close will fail if:
[EBADF] D is not an active descriptor.
SEE ALSO accept(2), flock(2), open(2), pipe(2), socket(2), socketpair(2), execve(2), fcntl(2)4th Berkeley Distribution May 22, 1986 CLOSE(2)