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 X11R4
cron
cron(1M) System Administration Commands cron(1M)NAME
cron - clock daemon
SYNOPSIS
/usr/sbin/cron
DESCRIPTION
cron starts a process that executes commands at specified dates and times.
You can specify regularly scheduled commands to cron according to instructions found in crontab files in the directory
/var/spool/cron/crontabs. Users can submit their own crontab file using the crontab(1) command. Commands which are to be executed only once
can be submitted using the at(1) command.
cron only examines crontab or at command files during its own process initialization phase and when the crontab or at command is run. This
reduces the overhead of checking for new or changed files at regularly scheduled intervals.
As cron never exits, it should be executed only once. This is done routinely by way of the svc:/system/cron:default service. The file
/etc/cron.d/FIFO file is used as a lock file to prevent the execution of more than one instance of cron.
cron captures the output of the job's stdout and stderr streams, and, if it is not empty, mails the output to the user. If the job does not
produce output, no mail is sent to the user. An exception is if the job is an at(1) job and the -m option was specified when the job was
submitted.
cron and at jobs are not executed if your account is locked. Jobs and processses execute. The shadow(4) file defines which accounts are not
locked and will have their jobs and processes executed.
Setting cron Jobs Across Timezones
The timezone of the cron daemon sets the system-wide timezone for cron entries. This, in turn, is by set by default system-wide using
/etc/default/init.
If some form of daylight savings or summer/winter time is in effect, then jobs scheduled during the switchover period could be executed
once, twice, or not at all.
Setting cron Defaults
To keep a log of all actions taken by cron, you must specify CRONLOG=YES in the /etc/default/cron file. If you specify CRONLOG=NO, no log-
ging is done. Keeping the log is a user configurable option since cron usually creates huge log files.
You can specify the PATH for user cron jobs by using PATH= in /etc/default/cron. You can set the PATH for root cron jobs using SUPATH= in
/etc/default/cron. Carefully consider the security implications of setting PATH and SUPATH.
Example /etc/default/cron file:
CRONLOG=YES
PATH=/usr/bin:/usr/ucb:
This example enables logging and sets the default PATH used by non-root jobs to /usr/bin:/usr/ucb:. Root jobs continue to use
/usr/sbin:/usr/bin.
The cron log file is periodically rotated by logadm(1M).
FILES
/etc/cron.d Main cron directory
/etc/cron.d/FIFO Lock file
/etc/default/cron cron default settings file
/var/cron/log cron history information
/var/spool/cron Spool area
/etc/cron.d/queuedefs Queue description file for at, batch, and cron
/etc/logadm.conf Configuration file for logadm
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO svcs(1), at(1), crontab(1), sh(1), logadm(1M), svcadm(1M), queuedefs(4), shadow(4), attributes(5), smf(5)NOTES
The cron service is managed by the service management facility, smf(5), under the service identifier:
svc:/system/cron:default
Administrative actions on this service, such as enabling, disabling, or requesting restart, can be performed using svcadm(1M). The ser-
vice's status can be queried using the svcs(1) command.
DIAGNOSTICS
A history of all actions taken by cron is stored in /var/cron/log and possibly in /var/cron/olog.
SunOS 5.10 5 Aug 2004 cron(1M)