10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
I need to develop a process/daemon which will constantly monitor a file for new entry and execute a command.
for eg, there is a file /var/log/inotify.log
When a new entry like below gets appeneded to this file, execute the command as follows.
/home/user/public_html/bad.php|CREATE
... (2 Replies)
Discussion started by: anil510
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2. Shell Programming and Scripting
Hi,
I am facing issues with the below:
I have a lookup file say lookup.lkp.This lookup.lkp file contains strings delimited by comma(,).
Now i want to read this command from file and execute it.
So my code below is :
Contents in the lookup.lkp file is :
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3. Shell Programming and Scripting
I am running the export command within a view to use that value inside my build script. But while executing it it is saying "export command not found"
My code is as follows:
--------------------------
#!/bin/sh
user="test"
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4. UNIX for Dummies Questions & Answers
Hi ,
I have to write a shell script to telnet to specific host and execute the admin command there. Please help me to do that.
Eg : telnet hostname portno
admin command
exit (3 Replies)
Discussion started by: arukuku
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5. Shell Programming and Scripting
Hi,
I've written a shell script to take photos with my camera.
After every picture taken, the picture is transmitted to the computer via usb and then deleted on the camera.
But sometimes there's an error and the picture is not deleted and so, after a certain time, the camera chip will be... (4 Replies)
Discussion started by: McLennon
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6. Shell Programming and Scripting
Hi ,
I am new to UNIX and Shell scripting . I am not able to execute a shell file . I try to do it using the below command.
./start.sh
but it shows an error that 'cannot execute ' what might be the reason for this? pls help me to resolve it. (1 Reply)
Discussion started by: Deepakkumard
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7. Shell Programming and Scripting
I don't know why the following shell script doesn't work. Could you please help me out?
#!/usr/bin/ksh
test="cal > /tmp/tmp.txt 2>&1"
$test
I know it will work for the following format:
#!/usr/bin/ksh
cal > /tmp/tmp.txt 2>&1
However, I need to get the command from the user in... (1 Reply)
Discussion started by: redtiger
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8. Shell Programming and Scripting
How do I suspend output of commands and tools that sometimes utter unwanted output? I know that I can always pipe to null or some such thing, but is there a simpler more elegant (i.e. accepted) practice? (4 Replies)
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9. UNIX for Dummies Questions & Answers
I need a user pause for a script file, like the pause command in dos. please help I thought it was the corn shell it is csh. (7 Replies)
Discussion started by: dennysavard
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10. Shell Programming and Scripting
Hi
I have this below script...I want to execute the shell command "rm" in the below script
but it is not working. Can anybody why so?
I got the below error
rm: /users/amvarma is a directory
sh: /*-log*: not found
-------------------
$u=`whoami`;
print "$u\n";
$op_1=$ARGV; # for... (0 Replies)
Discussion started by: amitrajvarma
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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)