hi i'm new to shell scripts and have a small problem
i am running a batch converter that returns all flash .flv files in a directory and create a png image from each one
the problem i have is the $1 variable , its ok on the first call but on the secound call $1.png , i have extra... (1 Reply)
I need to remove the entire file contents in file using the shell script.
Actually the grap -v command will create one more file and it occupy the space also.
I need to remove the entire file contents without creating new file using the shell scripting.
Please help me. (5 Replies)
Hey all. I am trying to write some scripts and need some assistance.
One:
I already have a script that appends lines to a file. I need a script that will remove those lines from that file, and have no idea how to go about doing this. Just need the command (if any) that can remove lines.
... (2 Replies)
The file starts like this:
Directory: <path to the script>
Script: <script fife name>
#!bin/ksh
##Comments
<actual script>
What is the use of the first two lines in the script? What if I save the file without them? What will be the effect? They are not comments. Im very new to this,... (4 Replies)
I want to make a config file which contain all the paths.
i want to read the config file line by line and pass as an argument on my below function.
Replace all the path with reading config path line by line and pass in respective functions.
how can i achieve that?
Kindly guide.
... (6 Replies)
Hi All, Looking for a quick LINUX shell script which can continuously monitors the flle size, report the process which is creating a file greater than certain limit and also kill that process. Can someone please help me on this? (4 Replies)
I wish to by pass a process if the file is over a certain size?
not sure this makes sense
current bit of the script below
#if we are bypAssing the OCR
if ; then
echo Bypassing HOTFOLDER OCR
HOT_FOLDER_DIR=$BATCH_POST_OCR_DIR;
potential change below? would this work would I need... (1 Reply)
Hello,
I have a src code file where I need to uncomment many lines.
The lines I need to uncomment look like,
C CALL l_r(DESNAME,DESOUT, 'Gmax', ESH(10), NO_APP, JJ)
The comment is the "C" in the first column. This needs to be deleted so that there are 6 spaces preceding "CALL".... (7 Replies)
Discussion started by: LMHmedchem
7 Replies
LEARN ABOUT CENTOS
flock
FLOCK(1) User Commands FLOCK(1)NAME
flock - manage locks from shell scripts
SYNOPSIS
flock [options] <file|directory> <command> [command args]
flock [options] <file|directory> -c <command>
flock [options] <file descriptor number>
DESCRIPTION
This utility manages flock(2) locks from within shell scripts or the command line.
The first and second forms wrap the lock around the executing a command, in a manner similar to su(1) or newgrp(1). It locks a specified
file or directory, which is created (assuming appropriate permissions), if it does not already exist. By default, if the lock cannot be
immediately acquired, flock waits until the lock is available.
The third form uses open file by file descriptor number. See examples how that can be used.
OPTIONS -s, --shared
Obtain a shared lock, sometimes called a read lock.
-x, -e, --exclusive
Obtain an exclusive lock, sometimes called a write lock. This is the default.
-u, --unlock
Drop a lock. This is usually not required, since a lock is automatically dropped when the file is closed. However, it may be
required in special cases, for example if the enclosed command group may have forked a background process which should not be hold-
ing the lock.
-n, --nb, --nonblock
Fail rather than wait if the lock cannot be immediately acquired. See the -E option for the exit code used.
-w, --wait, --timeout seconds
Fail if the lock cannot be acquired within seconds. Decimal fractional values are allowed. See the -E option for the exit code
used.
-o, --close
Close the file descriptor on which the lock is held before executing command . This is useful if command spawns a child process
which should not be holding the lock.
-E, --conflict-exit-code number
The exit code used when the -n option is in use, and the conflicting lock exists, or the -w option is in use, and the timeout is
reached. The default value is 1.
-c, --command command
Pass a single command, without arguments, to the shell with -c.
-h, --help
Print a help message.
-V, --version
Show version number and exit.
EXAMPLES
shell1> flock /tmp -c cat
shell2> flock -w .007 /tmp -c echo; /bin/echo $?
Set exclusive lock to directory /tmp and the second command will fail.
shell1> flock -s /tmp -c cat
shell2> flock -s -w .007 /tmp -c echo; /bin/echo $?
Set shared lock to directory /tmp and the second command will not fail. Notice that attempting to get exclusive lock with second
command would fail.
shell> flock -x local-lock-file echo 'a b c'
Grab the exclusive lock "local-lock-file" before running echo with 'a b c'.
(
flock -n 9 || exit 1
# ... commands executed under lock ...
) 9>/var/lock/mylockfile
The form is convenient inside shell scripts. The mode used to open the file doesn't matter to flock; using > or >> allows the lock-
file to be created if it does not already exist, however, write permission is required. Using < requires that the file already
exists but only read permission is required.
[ "${FLOCKER}" != "$0" ] && exec env FLOCKER="$0" flock -en "$0" "$0" "$@" || :
This is useful boilerplate code for shell scripts. Put it at the top of the shell script you want to lock and it'll automatically
lock itself on the first run. If the env var $FLOCKER is not set to the shell script that is being run, then execute flock and grab
an exclusive non-blocking lock (using the script itself as the lock file) before re-execing itself with the right arguments. It
also sets the FLOCKER env var to the right value so it doesn't run again.
EXIT STATUS
The command uses sysexits.h return values for everything else but an options -n or -w failures which return either the value given by the
-E option, or 1 by default.
AUTHOR
H. Peter Anvin <hpa@zytor.com>
COPYRIGHT
Copyright (C) 2003-2006 H. Peter Anvin.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
LAR PURPOSE.
SEE ALSO flock(2)AVAILABILITY
The flock command is part of the util-linux package and is available from Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils/util-
linux/>.
util-linux September 2011 FLOCK(1)