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BASH
This is an example of a very simple script: https://docs.google.com/document/d/1uNUGXkHmb9jvHA4Y12nTXEDSOjkLzzVoAcHkSVwxNmw/edit?usp=sharing
http://www.freeos.com/guides/lsst/while
Flow control: http://linuxcommand.org/wss0090.php
http://www.ieor.berkeley.edu/~faridani/bash.htm ←- notes
$# represents the number of arguments:
OR & AND OPERATORS FOR PROCESS FLOW “&& and || “
The right side of && will only be evaluated if the exit status of the left side is zero. || is the opposite: it will evaluate the right side only if the left side exit status is nonzero. You can consider [ … ] to be a program with a return value. If the test inside evaluates to true, it returns zero; it returns nonzero otherwise.
(ip route add 10.0.0.0/8 via 10.20.3.5 dev eth0 ; echo 'successful'; sleep 30 && ip route del 10.0.0.0/8 via 10.20.3.5 dev eth0) ping -c 1 $router_ip &>/dev/null || exit 0
IF
Comparisons: The following flags (preceded by minus), represent
- eq equal to
- ne not equal to
- lt less than
- le less than or equal to
- gt greater than
- ge greater than or equal to
File Operations: The following flags (preceded by minus), represent :
- s file exists and is not empty-f file exists and is not a directory
- d directory exists
- x file is executable
- w file is writable
- r file is readable
The tests below are test conditions provided by the shell:
- A file = True if the file exists.
- b file = True if the file exists and is block special file.
- c file = True if the file exists and is character special file.
- d file = True if the file exists and is a directory.
- e file = True if the file exists.
- f file = True if the file exists and is a regular file
- g file = True if the file exists and the set-group-id bit is set.
- k file = True if the files' “sticky” bit is set.
- L file = True if the file exists and is a symbolic link.
- p file = True if the file exists and is a named pipe.
- r file = True if the file exists and is readable.
- s file = True if the file exists and its size is greater than zero.
- s file = True if the file exists and is a socket.
- t fd = True if the file descriptor is opened on a terminal.
- u file = True if the file exists and its set-user-id bit is set.
- w file = True if the file exists and is writable.
- x file = True if the file exists and is executable.
- O file = True if the file exists and is owned by the effective user id.
- G file = True if the file exists and is owned by the effective group id.
- file1 –nt file2 = True if file1 is newer, by modification date, than file2.
- file1 ot file2 = True if file1 is older than file2.
- file1 ef file2 = True if file1 and file2 have the same device and inode numbers.
- z string = True if the length of the string is 0.
- n string = True if the length of the string is non-zero.
- string1 = string2 = True if the strings are equal.
- string1 != string2 = True if the strings are not equal.
- !expr = True if the expr evaluates to false.
- expr1 –a expr2 = True if both expr1 and expr2 are true.
- expr1 –o expr2 = True is either expr1 or expr2 is true.
CONDITIONAL CLAUSES
IF
test operators, see this link
#!/bin/bash if [ "foo" = "foo" ]; then echo expression evaluated as true fi
IN CLI (SINGLE LINE) - One-liner
conns=`ps aux|grep java|egrep '(IM|IDS)'|awk '{print $2}'`;for i in $conns;do netstat -tulpan|grep $i|grep "ESTABLISHED"|egrep '(10.23.54.5|10.23.47.196)';done
if [ "$2" != "" ]; then diff output$1 expected$1; fi
Run whatever command in a set of nodes defined in file list.txt
for in $i(cat list.txt); do ssh user@$i 'bash command'; done
EXECUTE SSH COMMAND IN A SET OF DEVICES FOR LOOP:
for host in $(seq --format='cc%02.0f' 01 17); do ssh $host "/sbin/ip link show|egrep '(em|eth|bond)[0-9]:' | cut -d: -f 2"| xargs -n 1 ssh $host ip link set mtu 9000 dev ; done
FOR
Examples:
for i in {1..5}; do COMMAND-HERE; done
for((i=1;i<=10;i+=2)); do echo "Welcome $i times"; done
if [ "$2" != "" ]; then diff output$1 expected$1; fi
if [ -s data/temp ]; then echo "EXISTS"; else echo "doesnt"; fi
To automatically generate configurations (configuration generator) from a single line in the CLI. See this example:
for i in {1..6}; do echo -e "conf t \n int fa0/0 \n ipv6 address 2001:150:1:$i::$i/128 \n no shut \n exit \n exit \n wr mem"; done
#!/bin/bash
while IFS=" " read -r val1 val2 rem
do
echo -e "
Host $val1
HostName $val1.dc.grapeshot.co.uk
User jaime_santos
Port 22";
done < ./input
This one applies actions to all file in a folder one-liner:
for f in *.mp3; do ffmpeg -i "$f" -vn -acodec libmp3lame -ac 2 -ab 160k -ar 48000 "encoded/${f%.avi}.mp4"; done
Small script with counter in for loop:
#!/bin/bash
t=1
for i in {189..204}
do echo "
${t}
set services nat rule r2 match-direction input
set services nat rule r2 term t$t from source-address 10.8.14.11/32
set services nat rule r2 term t$t then translated source-prefix 148.64.56.$i/32
set services nat rule r2 term t$t then translated translation-type basic-nat44";
t=$[t+1];
done
The counter variable is not initialized in the for but the whole range is defined beforehand.
for i in counter; do xxxx; done
http://www.cyberciti.biz/faq/bash-for-loop/
FOR cycle to generate repetitive text configuration file:
Observe that variable is simply defined inside script and FOR iterates the text substituting variable per each of the lines:
#!/bin/bash var=' one two three' for i in $var do echo 'This is the configuration I want to follow: '$i'; done
And I will repeat '$i' many times' done
CASE http://www.freeos.com/guides/lsst/ch03sec08.html
BASH IDIOMS:
Redirection ( stdout , stderr ). All files have an id (descriptor) but also! stdout1 , stderr2 habe ids!.
cat foo.txt 1> output.txt same as cat foo.txt 1> output.txt cat foo.txt 2> output.txt # only the error messages ls foo > /dev/null 2>&1 # 2>&1 you are basically saying “Redirect the stderr to the same place we are redirecting the stdout”. & is like the ind foo.txt > output.txt 2>&1 # out and err both to file and and screen > /dev/null 2>&1 # for the cron jobs. redirecting standard output into /dev/null, which is a place you can dump anything you don�t want (often called the bit-bucket), then redirecting standard error into standard output (you have to put an & in front of the destination when you do this).
cat << EOF > file.txt [text] EOF
Increment variable
$ x=$[x+1]
Add to numeric variables
num=`expr $num1 + $num2`
REGULAR EXPRESSIONS
http://www.zytrax.com/tech/web/regex.htm
Caret ^ : Beginning of the string
Dollar $: End of the string
READ ALL LINES IN A FILE:
value=0;
while read line do value=`expr $value + 1`; echo $line; done < "myfile"
echo $value;
while read UNDOFILE ; do FILE=$( echo "$UNDOFILE" | sed -r -e 's/.un~$//' -e 's&/\.([^/]*)&/\1&' ) ; [[ -e "$FILE" ]] || rm "$UNDOFILE" ; done
while read ADD ; do ping -c 3 $ADD -i 0.2 ; done < ./adds
—-
tester.sh
value="" while read line do value="$value | grep -v $line "; done < testex value="grep -i erro * $value > ~/errors_cleaned" # eval $value echo $value
cd vars/$folder grep -i erro * > ~/errors.txt grep -i excep * > ~/exceptions.txt grep -i warnin * > ~/warnings.txt
Test if the result of a serch is not empty:
RESULT=$(find . -type f -mtime +1 | grep -v '/\.' | grep -v '.gz') echo $RESULT if [ ! -z "$RESULT" ] ; then gzip $RESULT else echo "nothing to do" fi
Read lines from two files and concatenate interleaved results (see 1.tar attached)
START='tcpdump -ni eth1 -s 0 -C 100 -W 100 -w /home/jaime.santos/test/test vlan 4001 and (host 94.142.191.6 or (vlan and host 94.142.191.6))'ps -ef|grep -v grep|grep -F "$START" >/dev/null 2>&1
case “$?” in
0) $NOP ;; 1) $START >/dev/null 2>&1 & #NOTICE=/tmp/watchdog.txt #echo "$NAME was not running and was started on `$DATE`" > $NOTICE #$MAIL -n -s "watchdog notice" -c $NOTIFYCC $NOTIFY < $NOTICE #$RM -f $NOTICE ;; esac
exit
FIND TRADES (FIELDS 150=D) IN TODAY'S TRADES
find . -mtime -1 -exec cat -A {} \; | egrep "150=F"
CONFIGURATION SCRAPING
See the script named “bash_config_scraping1.tar.gz” attached
TO EVALUATE COMMANDS REMOTELY (SSH)
ssh root@jaguar27.dc.grapeshot.co.uk "/usr/bin/sed -i '/^IPADDR=/d' /etc/sysconfig/network-scripts/ifcfg-bond0"
SEND FILE IN RUNTIME - HEREDOC
With substitution:
#!/bin/bash fruit='ONION' cat <<EOF | ssh -p 5201 192.168.0.5 'cat - > /tmp/my_remote_file.txt' apple $fruit green tree EOF
Without substitution:
#!/bin/bash fruit='ONION' cat <<'EOF' | ssh -p 5201 192.168.0.5 'cat - > /tmp/my_remote_file.txt' apple $fruit green tree EOF
