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dynamic date value in shell scripts using a variable – easier to read in scripts: NOW=$(date +”%Y%m%d%H%M%S”) echo “bar” > “$NOW”foobar.txt one-line, equivalent to above: echo “bar” > $(date +”%Y%m%d%H%M%S”)foobar.txt alternate single-line format: echo “bar” >> $(date “+myfile%Y%m%d.txt”) man strftime to see formatting values Calculating percentages in bash Dividing in bash will cause problems if the result is below zero. This is a problem when you’re trying to work out percentages. For example, if you simply want to divide 1 by 2 the result should be 0.5. However, bash returns the result 0: user@computer:~> echo $(( 1 / 2 […] #!/bin/bash # max_number_of_ssh_client max_number_of_ssh_client=3 # lsof is essential if [[ ! -x `which lsof` ]]; then yum install lsof -y RETVAL=$? if [[ “$RETVAL” -ne “0” ]]; then echo “ERROR: can NOT use lsof command, please check your internet connection or install lsof by manual! ” exit $RETVAL fi else # TODO # for awk, […] Clear contents of a file in UNIX $cat /dev/null > file or $true > file This works with AIX df -g | egrep -v “Filesystem|proc|tmp” | sed ‘s/\%//’ | awk ‘$4 >= 90 {print $4 “%\t” $7}’ df -k | sed 1d | awk ‘$4>90 {print}’ This works with Solaris and Linux df -k | egrep -v “proc|fd|cdrom|mnttab|run|tmp|Filesystem” | sed ‘s/\%//’ | awk ‘$5 >= 90 {print $5 “%\t” $6}’ #!/bin/bash for ((i=1;i<=254;i++)) do ip=192.168.1.$i ping $ip -c 1 |grep -q ‘ttl=’ && echo “$ip” >> alive.txt done #!/bin/bash groupadd websphere for user in app1 app2 app3 app4 do useradd -g websphere -s /sbin/nologin -d /dev/null $user (echo $user;echo $user) | smbpasswd -s -a $user done cat access.log |awk ‘{print $1}’|sort |uniq -c |sort -nr […] [gview file=”http://rmohan.com/wp-content/uploads/2015/05/unix_tutorial.pdf”] Shell program View System Date, Calender Calender [root@cluster1 ~]# cal April 2015 Su Mo Tu We Th Fr Sa 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 [root@cluster1 ~]# cal 7 2015 July […] SHELL SCRIPTING: -shell is a command line interpreter -it is interface b/w user & kernel – it takes commands form the user and excute them Shell are different types: Shell developed shellprompt executetioncommand Bourne SteveBorn $ sh Corn devidCorn $ ksh Cshell billjoy % csh Bash born $ sh(or)bsh Zsh panel $ zsh Shell variables: […] NAME tee – read from standard input and write to standard output and files SYNOPSIS tee [OPTION]… [FILE]… DESCRIPTION Copy standard input to each FILE, and also to standard output. -a, –append append to the given FILEs, do not overwrite -i, –ignore-interrupts ignore interrupt signals –help display this help and exit –version output version information […] |
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