Commands by zlemini

Commands by zlemini (44)

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Retrofit a shebang to an existing script

Function to add a shebang to an existing script, handy if you forgot to add it in the first place. Show Sample Output
This is sample output - yours may be different.
```
$ shebang "/bin/bash" test.sh

$ shebang $(which python) test.py
```
1

shebang () { printf '%s\n' 0a '#!'"$1" . w | ed -s "$2" ; }

zlemini · 2017-03-20 19:14:41 18
Count lines in a file with grep

Returns the number of lines in a file, emulates "wc -l" behavior with grep.
This is sample output - yours may be different.
1

grep -c ".*" filename

zlemini · 2016-10-26 22:32:23 16
Replace the content of an XML element

Replaces "650" with "999" in simple.xml. xml used - http://www.w3schools.com/xml/simple.xml
This is sample output - yours may be different.
1

xmlstarlet ed -u '//food[calories="650"]/calories' -v "999" simple.xml

zlemini · 2016-10-05 18:29:01 18
Use a regex as a field separator awk
This is sample output - yours may be different.
2

echo one 22 three | awk -F'[0-9][0-9]' '{print $2}'

zlemini · 2016-01-20 21:11:08 12
Preserve user variables when running commands with sudo.

In this case the current user has proxy variable set which allows access to the rpm on the internet but needs root privs to install it. Running sudo -E preserves the current user proxy var and allows the rpm install to be executed with sudo.
This is sample output - yours may be different.
1

sudo -E rpm -Uvh "http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm"

zlemini · 2015-10-29 14:06:48 10
Determine if a port is open with bash

For times when netcat isn't available. Will throw a Connection refused message if a port is closed. Scriptable: (: </dev/tcp/127.0.0.1/80) &>/dev/null && echo "OPEN" || echo "CLOSED"
This is sample output - yours may be different.
14

: </dev/tcp/127.0.0.1/80

zlemini · 2015-08-28 19:07:27 18
Search replace with Ansible style timestamps

ls httpd.conf httpd.conf.2015-07-22@14:43:20
This is sample output - yours may be different.
1

sed -i.$(date +%F@%T) 's/^LogLevel warn/LogLevel debug/g' httpd.conf

zlemini · 2015-07-22 14:47:26 10
Get HTTP status code with curl AND print response on new line
This is sample output - yours may be different.
1

curl -s -o /dev/null -w "%{http_code}\n" localhost

zlemini · 2014-11-06 22:43:18 19
Null a file with sudo
This is sample output - yours may be different.
2

sudo bash -c "> /var/log/httpd/access_log"

zlemini · 2014-10-02 15:39:47 12
Clone perms and owner group from one file to another

Copy both perms and owner group from one file to another.
This is sample output - yours may be different.
2

for i in chmod chown; do sudo "$i" --reference=/home/user/copyfromfile /tmp/targetfile; done

zlemini · 2014-08-28 15:08:32 8
Hits per hour apache log
This is sample output - yours may be different.
2

awk -F: '{print $2}' access_log | sort | uniq -c

zlemini · 2014-07-29 15:09:27 4
Run a script in parrallel over ssh

Runs a local script over ssh assuming ssh keys are in place. -P argument prints results to stdout. # Uses - https://code.google.com/p/parallel-ssh/
This is sample output - yours may be different.
1

pssh -h RemoteHosts.txt -P -I < ~/LocalScript.sh

zlemini · 2014-07-14 16:02:12 6
Prepend a text to a file.

Syntax: $ prepend content to add [filename] Uses ed, so no temp files created.
This is sample output - yours may be different.
3

prepend () { array=("$@"); len=${#array[@]}; file=${array[$len-1]}; text=${array[@]:0:$len-1}; printf '%s\n' 0a "$text" . w | ed -s "$file"; }

zlemini · 2013-12-09 21:59:26 8
Extract busiest times from apache access log

Analyze an Apache access log for the time period with most activity and display the hit count, requesting IP and the timestamp. May help detect a brute force dos attack.
This is sample output - yours may be different.
2

cut -d " " -f1,4 access_log | sort | uniq -c | sort -rn | head

zlemini · 2013-09-20 21:29:32 12
Fetch the current human population of Earth
This is sample output - yours may be different.
5

curl -s http://www.census.gov/popclock/data/population/world | awk -F'[:,]' '{print $7}'

zlemini · 2013-07-28 00:31:30 10
Oneliner to run commands on multiple servers

Oneliner to run commands on multiple servers over ssh. - First parameter "$1" is the command you want to execute remotely. ( It can be multiple commands e.g. "hostname;uptime") - Second parameter "${@:2}" represents the remote host/s you want to run the command/s on. Show Sample Output
This is sample output - yours may be different.
```
$ sxh "hostname;uptime" Host1 Host2
Host1
 11:25am  up 7 days,  4:42,  0 users,  load average: 0.09, 0.08, 0.05
Host2
 11:25am  up 7 days,  4:34,  1 user,  load average: 0.00, 0.00, 0.01
```
2

sxh () { for i in "${@:2}"; do ssh "$i" "$1"; done ; }

zlemini · 2013-04-12 11:34:02 9
Function to change prompt

Bash function to change your default prompt to something simpler and restore it to normal afterwards. Show Sample Output
This is sample output - yours may be different.
```
Custom prompt 13:22:50 $ prompt off
$ 
$ prompt on
Custom prompt 13:22:54 $
```
1

prompt (){ if [ "$1" = "on" ]; then . ~/.bash_profile; else if [ "$1" = "off" ];then PS1="$ ";fi;fi; }

zlemini · 2013-02-17 13:41:18 8
diff files ignoring comments and blank lines (lines starting with #)
This is sample output - yours may be different.
0

diff -BI '^#' file{1,2}

zlemini · 2013-02-17 11:53:41 45
List all available python modules
This is sample output - yours may be different.
1

python -c "help('modules')"

zlemini · 2013-01-13 15:10:23 5
Change a specific value in a path

Awk replaces the value of a specific field while retaining the field separator "/" . Show Sample Output
This is sample output - yours may be different.
```
$ echo /home/foo/dir1/bar |  awk -F/ -v OFS=/ '{$3 = "dir2"}1'
/home/foo/dir2/bar
```
1

echo /home/foo/dir1/bar | awk -F/ -v OFS=/ '{$3 = "dir2"}1'

zlemini · 2012-10-26 16:17:20 16
grep lines containing two consecutive hyphens
This is sample output - yours may be different.
2

grep -- -- file

zlemini · 2012-08-08 21:40:21 39

This inserts an element as last child under /breakfast_menu/food in simple.xml. xml used - http://www.w3schools.com/xml/simple.xml Show Sample Output

xmlstarlet ed -s "/breakfast_menu/food" -t elem -n 'foo' -v "bar" simple.xml

zlemini · 2012-06-03 18:35:53 15

Perl oneliner to print access rights in octal format

This prints file access rights in octal - useful when "stat" is unavailable. Show Sample Output
This is sample output - yours may be different.
```
$ perl -e 'printf "%04o\n", (stat shift)[2] & 0777;' /etc/passwd
0444
```
1

perl -e 'printf "%04o\n", (stat shift)[2] & 0777;' file

zlemini · 2012-03-22 15:05:04 10
Transfer a file to multiple hosts over ssh

You can push files to up to 32 servers at once assuming ssh keys are in place. Great tool, it is part of the pssh suite.
This is sample output - yours may be different.
13

pscp -h hosts.txt -l username /etc/hosts /tmp/hosts

zlemini · 2012-01-24 12:19:30 11
tail a log over ssh

This is also handy for taking a look at resource usage of a remote box. ssh -t remotebox top
This is sample output - yours may be different.
13

ssh -t remotebox "tail -f /var/log/remote.log"

zlemini · 2011-12-12 20:24:23 6
1 2 >

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python smtp server

This command will start a simple SMTP server listening on port 1025 of localhost. This server simply prints to standard output all email headers and the email body.

Find longest running non-root processes on a machine

If you have ever been trying to look for a list of processes based on their elapsed time you don't need to look any further. This command lets you find the list of processes ordered in a reversed order (oldest at the top) that have been running for over an hour on your system. Any system processes are filtered out, leaving only user initiated ones in. I find it extremely useful for debugging and performance analysis.

Automatically find and re-attach to a detached screen session

man screen: "-D -R Attach here and now. In detail this means: If a session is running, then reattach. If necessary detach and logout remotely first. If it was not running create it and notify the user. This is the author?s favorite."

Shows how many percents of all avaliable packages are installed in your gentoo system

Fix the vi zsh bindings on ubuntu

Use sed to comment out any up/down bindings in zsh

Search commandlinefu.com from the command line using the API

just like the original - just colored and with less

Find the package that installed a command

Convert seconds to [DD:][HH:]MM:SS

Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

ring the bell

Get your outgoing IP address

should be very consistent cause it's google :-)

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