"--" is not a grep-specific syntax. That's a standard feature in option processing. If you need to pass an argument to a command and that argument begins with a dash, it will be interpreted as an option. To work around that scenario, "--" tells the option processing code that there are no more options to process.
You can try it yourself with different tools (rm, cp, etc). Create a file whose name begins with dash and try to pass it as an argument. It will fail to run with an unrecognized option error, if you're lucky. If you're unlucky, it will run with unintended consequences. To do it properly, you'll need to precede the filename with "--".
Hi Guys,
I need to set the value of $7 to zero in case $7 is NULL. I've tried the below command but doesn't work. Any ideas. thanks guys.
MEM=`ps v $PPID| grep -i db2 | grep -v grep| awk '{ if ( $7 ~ " " ) { print 0 } else { print $7}}' `
Harby. (4 Replies)
Hello,
I looking to use grep to return a string with exactly n matches.
I'm building off this:
ls -aLl /bin | grep '^.\{9\}x' | tr -s ' '
-rwxr-xr-x 1 root root 632816 Nov 25 2008 vi
-rwxr-xr-x 1 root root 632816 Nov 25 2008 view
-rwxr-xr-x 1 root root 16008 May 25 2008... (7 Replies)
Hello,
I'm working on unix with grep (GNU grep) 2.5.1. I'm going through some of the newer regex syntax using Regular Expression Reference - Advanced Syntax a guide.
ls -aLl /bin | grep "\(x\)"
Which works, just highlights 'x' where ever, when ever.
I'm trying to to get (?:) to work but... (4 Replies)
Hi All, I need to grep few files which has words like the below in the file name , which i want to put it in a file and and grep for the files which contain these names and move it to a new directory ,
full file name -C20091210.1000-20091210.1100_SMGBSC3:1000... (2 Replies)
Hi All,
Please i need to know the difference between grep, egrep & grep -i when used to serach through a file.
My platform is SunOS 5.9 & i'm using the korn shell.
Regards,
- divroro12 - (2 Replies)
I have a directory I need to grep which consists of numbered sub directories. The sub directory names change daily. A file resides in this main directory that shows which sub directories are FULL backups or INCREMENTAL backups.
My goal is to grep the directory for the word "full" and then... (2 Replies)
Hello.
I want to get all modules which are loaded and which name are exactly 2 characters long and not more than 2 characters and begin with "nv"
lsmod | (e)grep '^nv????????????
I want to get all modules which are loaded and which name begin with "nv" and are 2 to 7 characters long
... (1 Reply)
Hi,
I have a number of files containing the information below.
"""""
Fundallinfo
6.3950 14.9715 14.0482
"""""
I would like to grep for Fundallinfo and use it to read the next line? I ideally would like to read the three numbers that follow in the next line and... (2 Replies)
i have this line of code that looks for the same file if it is currently running and returns the count.
`ps -eaf -o args | grep -i sfs_pcard_load_file.ksh | grep -v grep | wc -l`
basically it is assigned to a variable
ISRUNNING=`ps -eaf -o args | grep -i sfs_pcard_load_file.ksh |... (6 Replies)
Discussion started by: wtolentino
6 Replies
LEARN ABOUT LINUX
mail-lock
lockfile-progs(1) Lockfile programs lockfile-progs(1)NAME
lockfile-progs - command-line programs to safely lock and unlock files and mailboxes (via liblockfile).
SYNOPSIS
mail-lock [--use-pid] [--retry retry-count]
mail-unlock
mail-touchlock [--oneshot]
lockfile-create [--use-pid] [--retry retry-count] [--lock-name] filename
lockfile-remove [--lock-name] filename
lockfile-touch [--oneshot] [--lock-name] filename
lockfile-check [--use-pid] [--lock-name] filename
DESCRIPTION
Lockfile-progs provides a set a programs that can be used to lock and unlock mailboxes and files safely (via liblockfile):
mail-lock - lock the current user's mailbox
mail-unlock - unlock the current user's mailbox
mail-touchlock - touch the lock on the current user's mailbox
lockfile-create - lock a given file
lockfile-remove - remove the lock on a given file
lockfile-touch - touch the lock on a given file
lockfile-check - check the lock on a given file
By default, the filename argument refers to the name of the file to be locked, and the name of the lockfile will be filename .lock. How-
ever, if the --lock-name argument is specified, then filename will be taken as the name of the lockfile itself.
Each of the mail locking commands attempts to lock /var/spool/mail/<user>, where <user> is the name associated with the effective user ID,
as determined by via geteuid(2).
Once a file is locked, the lock must be touched at least once every five minutes or the lock will be considered stale, and subsequent lock
attempts will succeed. Also see the --use-pid option and the lockfile_create(3) manpage.
The lockfile-check command tests whether or not a valid lock already exists.
OPTIONS -q, --quiet
Suppress any output. Success or failure will only be indicated by the exit status.
-v, --verbose
Enable diagnostic output.
-l, --lock-name
Do not append .lock to the filename. This option applies to lockfile-create, lockfile-remove, lockfile-touch, or lockfile-check.
-p, --use-pid
Write the current process id (PID) to the lockfile whenever a lockfile is created, and use that pid when checking a lock's validity.
See the lockfile_create(3) manpage for more information. This option applies to lockfile-create, lockfile-remove, lockfile-touch, and
lockfile-check.
-o, --oneshot
Touch the lock and exit immediately. This option applies to lockfile-touch and mail-touchlock. When not provided, these commands will
run forever, touching the lock once every minute until killed.
-r retry-count, --retry retry-count
Try to lock filename retry-count times before giving up. Each attempt will be delayed a bit longer than the last (in 5 second incre-
ments) until reaching a maximum delay of one minute between retries. If retry-count is unspecified, the default is 9 which will give
up after 180 seconds (3 minutes) if all 9 lock attempts fail.
EXAMPLES
Locking a file during a lengthy process:
lockfile-create /some/file
lockfile-touch /some/file &
# Save the PID of the lockfile-touch process
BADGER="$!"
do-something-important-with /some/file
kill "${BADGER}"
lockfile-remove /some/file
EXIT STATUS
0
For lockfile-check this indicates that a valid lock exists, otherwise it just indicates successful program execution.
Not 0
For lockfile-check a non-zero exit status indicates that the specified lock does not exist or is not valid. For other programs it
indicates that some problem was encountered.
SEE ALSO maillock(3)touchlock(3)mailunlock(3)lockfile_create(3)lockfile_remove(3)lockfile_touch(3)lockfile_check(3)AUTHOR
Written by Rob Browning <rlb@defaultvalue.org>
0.1.12 2008-02-10 lockfile-progs(1)