Please explain the usage of ampersand in the following command
What I understand is that ampersand is used to run some process in the background. And, what I am expecting from this command is
"Output of who should be displayed on the screen with value of total number of users who have logged in displayed at the bottom of the list."
how can I find cpu usage memory usage swap usage and
I want to know CPU usage above X% and contiue Y times and memory usage above X % and contiue Y times
my final destination is monitor process
logical volume usage above X % and number of Logical voluage above
can I not to... (3 Replies)
Hi,
I have this line in a script:
if mt -f /dev/nst0 rewind > /tmp/status_nst0.log 2>&1 ; then
What does the 2>&1 mean? I think the line is saying that after rewinding the device if the log file does not exist then execute the code but I do not understand the contribution of the 2>&1.... (2 Replies)
Hi,
By using time command we can determine the execution time of a process or command.
bash-2.04$ time ls -l
total 0
-rw-r--r-- 1 admin tac 0 Oct 6 04:46 file1
-rw-r--r-- 1 admin tac 0 Oct 6 04:46 file2
real 0m0.002s
user 0m0.000s
sys 0m0.001s... (5 Replies)
Hi,
17 11 * * * /xx/yy/name.sh >> /tmp/cron.log 2>&1
The above statement is one of the crontab entries.
The crong log is getting appended everytime. Can anyone tell me the usage of "2>&1"?
Thanks. (2 Replies)
Hi all,
Can you please tell me the command, with which one can know the amount of space a specific directory has used.
df -k . ---> Displays, the amount of space allocated, and used for a directory.
du -k <dir name> - gives me the memory used of all the files inside <dir>
But i... (2 Replies)
In the terminal, using the ampersand allows the process to run in the background--Emacs, for example. But is there a way to automatically open Emacs as a background process so I can still use the command line? Typing the ampersand is just annoying to me, and I keep forgetting; it's just too useful... (0 Replies)
I have the following line of code that works wonders. I just don't completely understand it as I am just starting to learn regex. Can you help me understand exactly what is happening here?
find . -type f | grep -v '^\.$' | sed 's!\.\/!!' (4 Replies)
Hi all,
Been reading a lot of the cpu load and its "analogy of it to car traffic path of expressway"
From wiki
Most UNIX systems count only processes in the running (on CPU) or runnable (waiting for CPU) states. However, Linux also includes processes in uninterruptible sleep states... (13 Replies)
Hello everybody,
I have a Problem with sed command.
I want to replace a defined string with a string from a database field (dynamic).
e.g.
sed -i -e 's/%NAME%/'"$HNAME"'/g'
The Problem is that the $HNAME variable can contain Special characters like '&'
e.g.
HNAME="AH Kruger & Co. KG"
... (1 Reply)
For years I have spawned shell scripts with nohup and ampersand and they run whether or not I stay logged in. Recently a client told us that we had to set a keep alive timeout on all of our Redhat 7.6 Linux servers. Our sysadmin set the following parameters in the sshd_config file on all of our... (10 Replies)
Discussion started by: gandolf989
10 Replies
LEARN ABOUT CENTOS
shell-quote
SHELL-QUOTE(1) User Contributed Perl Documentation SHELL-QUOTE(1)NAME
shell-quote - quote arguments for safe use, unmodified in a shell command
SYNOPSIS
shell-quote [switch]... arg...
DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands
or files with embedded white space or shell globbing characters safely. Here are a few examples.
EXAMPLES
ssh preserving args
When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and
passes them to "$SHELL -c". This doesn't work as intended:
ssh host touch 'hi there' # fails
It creates 2 files, hi and there. Instead, do this:
cmd=`shell-quote touch 'hi there'`
ssh host "$cmd"
This gives you just 1 file, hi there.
process find output
It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to
split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote:
eval set -- `find -type f -print0 | xargs -0 shell-quote --`
debug shell scripts
shell-quote is better than echo for debugging shell scripts.
debug() {
[ -z "$debug" ] || shell-quote "debug:" "$@"
}
With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can.
save a command for later
shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command
you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are
things the user can't pass through), you can do something like this:
user_switches=
while [ $# != 0 ]
do
case x$1 in
x--pass-through)
[ $# -gt 1 ] || die "need an argument for $1"
user_switches="$user_switches "`shell-quote -- "$2"`
shift;;
# process other switches
esac
shift
done
# later
eval "shell-quote some-command $user_switches my args"
OPTIONS --debug
Turn debugging on.
--help
Show the usage message and die.
--version
Show the version number and exit.
AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions.
AUTHOR
Roderick Schertler <roderick@argon.org>
perl v5.16.3 2010-06-11 SHELL-QUOTE(1)