Find and remove files
I regularly use the find command in scripts to clean directories on my servers.
The common way to use find to do this is to write something like:
find ./my_dir -name 'cache-*' -exec rm -rf \{\} \;
It works fine but it always outputs messages like this:
find: ./mydir/cache-001: No such file or director
which can be annoying when ran in a crontab.
I just found recently that using the option ‘-delete’ with find just fix this problem.
find ./my_dir -name 'cache-*' -delete
This entry was written by , posted on February 4, 2010 at 11:36 am, filed under Command line and tagged find. Leave a comment or view the discussion at the permalink.
Quickly check hosts with ping
I needed a script for a quick health check of a bunch of servers.
This is how I did it using the ping command:
for((i=1;i<42;i++)); do
ping -c 1 -W 3 host${i}.domain.com &> /dev/null
if [ $? -ne 0 ] ; then
echo "host${i} is down"
else
echo "host${i} is up"
fi
done
You can also use netcat and check a specific port:
netcat -z -w 2 host${i}.domain.com 80 &> /dev/null
This entry was written by , posted on August 14, 2009 at 1:46 pm, filed under Command line and tagged loop, netcat, ping. Leave a comment or view the discussion at the permalink.
Set Terminal tab title in Mac OS X
I wrote previously a how-to to set your iTerm tab title.
I finally found a tool to do the same thing with the default Mac OS X Terminal.
Check it out here, it works perfectly for me!
This entry was written by , posted on August 11, 2009 at 2:12 pm, filed under Command line and tagged shell, terminal. Leave a comment or view the discussion at the permalink.
Finding the total size of a set of files with awk
If you need to sum the total size of files in a directory or matching a pattern, an easy solution is to use awk.
I needed to calculate this total for a set of javascript files, I used this command line:
$ find App/ -name '*.js' -exec ls -l \{\} \; | awk '{sum+=$5} END {print sum}'
1929403
For a human readable result, you can divide your result and use printf to format it:
$ find App/ -name '*.js' -exec ls -l \{\} \; | awk '{sum+=$5} END {printf("%.2fM\n", sum/1024/1024)}'
1.84M
This entry was written by , posted on April 17, 2009 at 11:12 am, filed under Command line and tagged awk. Leave a comment or view the discussion at the permalink.
Memory usage by group of processes
While monitoring a http/php server, I needed to do some statistics about php-cgi memory usage.
Playing with memory_limit in PHP, we wanted to know the average memory usage per php-cgi process. This is easily calculated with our best friend awk.
First, get the number of php running processes:
# ps aux | grep php-cgi | grep -v grep | wc -l 126
Then, use awk to calculate the average memory usage for these processes:
# ps aux | grep --exclude=grep php-cgi | grep -v grep | awk 'BEGIN{s=0;}{s=s+$6;}END{print s/126;}'
33987.8
The number used in the calculation is the field RSS given by ps. The ps manual page says:
rss: resident set size, the non-swapped physical memory that a task has used (in kiloBytes)
You can also calculate the total memory used by all php-cgi processes:
# ps aux | grep --exclude=grep php-cgi | grep -v grep | awk 'BEGIN{s=0;}{s=s+$6;}END{print s;}'
4302028
If you need to watch the trend of this average memory usage, a little shell loop does the trick:
# while [ 1 ]; do ps aux | grep --exclude=grep php-cgi | grep -v grep | awk 'BEGIN{s=0;}{s=s+$6;}END{print s/126;}'; sleep 2; done
34401.3
34405.1
34408.4
34409.4
34414.2
34417
This entry was written by , posted on March 13, 2009 at 4:14 pm, filed under Benchmarks, Command line, Monitoring and tagged awk, memory, php, shell. Leave a comment or view the discussion at the permalink.
The unix touch command
This post is a quick ref on the linux touch command. All the examples have been tested on Linux.
This command is used to update the access and modification times of files.
- touch’s syntax
touch [option] file_name(s) touch file1 file2 file3
- Here some examples:
# touch /tmp/file # ls -l /tmp/file rw-r--r-- 1 charlybr charlybr 0 Sep 10 16:13 /tmp/file
- Update access and modification time to current time:
# ls -l /tmp/file rw-r--r-- 1 charlybr charlybr 0 Sep 10 16:13 /tmp/file # touch /tmp/file # ls -l /tmp/file rw-r--r-- 1 charlybr charlybr 0 Sep 10 16:14 /tmp/file
- Update access and modification time to a specified timestamp ([[CC]YY]MMDDhhmm[.ss] format):
# touch -t 09091842 /tmp/file # ls -l /tmp/file -rw-r--r-- 1 charlybr charlybr 0 Sep 9 18:42 /tmp/file
- Update access and modification time to a specified date
# touch -d '9 Sep' /tmp/file # ls -l /tmp/file -rw-r--r-- 1 charlybr charlybr 0 Sep 9 00:00 /tmp/file # touch -d '9 Sep 2008 13:14' /tmp/file # ls -l /tmp/file -rw-r--r-- 1 charlybr charlybr 0 Sep 9 13:14 /tmp/file
Links
- touch is part of the Coreutils package
- touch documentation page
- man page on FreeBSD
This entry was written by , posted on September 11, 2008 at 7:30 am, filed under Command line and tagged coretutils, shell. Leave a comment or view the discussion at the permalink.
Retrieve file from svn
Sometimes you need to retrieve a single file from SVN without doing a checkout on the repository.
SVN provides the svn cat to output the content of a file. You can redirect the output to get the file as :
svn cat https://svn.mydomain.com/project/folder/file.ext > file.ext
You can also use a simple shell script to do the work :
$ cat svnget
#!/bin/sh
if [ -z "$1" ]; then
echo
echo "Usage : $0 <SVN-URL>"
echo
exit
fi
fn=`basename $1`
svn cat $1 > $fn
This entry was written by , posted on May 23, 2008 at 7:51 am, filed under Command line and tagged svn. Leave a comment or view the discussion at the permalink.
Automatically set title on iTerm tabs
If like me you use iTerm for your terminal sessions, this is the tips to dynamically set the tab title.
As I’m using the bash shell, the tab title can be automatically set with the PROMPT_COMMAND variable. You can set this variable in /etc/profile or in your .bashrc
Mine is like this :
export PROMPT_COMMAND=’echo -ne “\033]0;${USER}@${HOSTNAME%%.*}\007″‘
The content of the variable is executed each time bash prints your prompt. Here echo is executed with the escape sequence to set the term title.
More informations
Some readings about this subject :
This entry was written by , posted on May 7, 2008 at 2:10 pm, filed under Command line and tagged bash, iTerm. Leave a comment or view the discussion at the permalink.
Command line history
As read here, this is my command line history on my MacBook :
62 cd
55 scp
33 for
28 vim
25 ping
17 history
13 ls
4 sudo
3 telnet
This entry was written by , posted on May 2, 2008 at 5:54 pm, filed under Command line and tagged history. Leave a comment or view the discussion at the permalink.