find Command

1. find Command • Characteristics • Locate files descending from multiple starting points • Employs regular expressions • Examples On entire system: >find / -name "cs*" Two starting points: >find /usr /var/html –name "cs*" Case insensitive: >find /usr –iname "*htm*" More than 3 days ago: >find /usr -mtime +3 –name "*htm*" Within the last 3 days: >find /usr –mtime -3 –name "*htm*"

2. Customizing your prompt • To set: set $PS1 variable with a prompt string. • Additional prompt string capabilities:\d = todays date\H = host name\T = current time\w = working directory\! = history number of this command • Example: export PS1=">" • Example: export PS1="\! \w >"

3. Disk Usage Commands • Free Blocks: >df • Disk usage • Size of each directory (recursive): >du • Summary of each directory (not recursive):>du –s * • Size of a single directory: >du –s <fileName> • Sort usage, numeric reverse, page at a time>du | sort –nr | more

4. Aliases Replace a word by a string when starting a command • Definition: Replace a string by a word at the start of a command • Use: Shorten what needs to be typed by aliasing a command with its arguments • Use: Rename a command to something more familiar • Examples • Display all of the aliases in use: >alias • Example (dos user directory list): >alias dir='ls –l' • To remove an alias: >unalias dir

5. Creating Script Variables • create a variable: <var>="value" • Note: do not use spaces • Example: >TEAM="Yanks" >echo $TEAM • Variables are case sensitive • You can use variables anywhere in commnads >bindir=~bin >echo $bindir • To make variables accessible to all sub shells, use export: >export TEAM="yanks"

6. Command Substitution The output of one command becomes part of another • Setting variables: `<cmd>` or $(<cmd>) • Examples • >dir=`pwd`>echo $dir • files=$(ls)echo $files • echo there are `grep –ci bush grades` bush\'s • From command line: `<cmd>`echo `date`grep "abc" `cat file.txt` Note: echo “$(ls)” preserves the new lines in the output Note: The back quote is found on the top left of most keyboards

7. $PATH Environment Variable • Most unix commands are C programs • When you execute a command • $PATH contains a series of path names • The shell searches all variables in $PATH • To add program/bin to the $PATH variableexport PATH = $PATH:program/bin • To add the current directory to $PATHexport PATH = $PATH:.

8. Shell Scripts See Bash's Beginners guide See examples on the class web site • Put multiple commands in a file and then execute them by typing the file name • They execute the statements one by one • Creating a script • The first line should be #!/bin/bash • Other lines starting with # are comments • Make executable: u+x scriptName • Execute: ./scriptName [unless working directory is in the search path] • Use script capabilities to • create loops • create decisions • write functions

9. Arguments to a Shell Script • Arguments to a script • $0 is the name of the shell script (argument 0) • $1 is the first argument • $2 is the second argument • $k is the kth argument • $# is the number of arguments • $@ is all of the arguments • Example: scriptFile x y z • $0 = scriptFile • $2 = y • $# is 3 • $@ is x y z

10. Shell Script Decisions if [ condition ]; then <statements> fi if [ condition ]; then <statements> else fi if [ $1 == 3 ] ; then echo "arg equals 3" else echo "arg not 3"; fi Note: space after [ and before ], semi colon after ] Comparators: ! -lt –le –gt –ge –f == -r where -f is file –r for readable file

11. while and do Loops while [ condition ]; do command1; command2; command3 done i=0 while [ $i –lt 4 ]; do echo "Welcome $i"; i=$[$i+1]; done or i=0 do until [ $i == 4 ]; do echo "Welcome $i"; i=$[$i+1]; done or i=0 while [ $i –lt 4 ]; do echo "Welcome $i" i=$[$i+1] done Semicolons separate parts of the loop on the same line Boolean variables true or false are legal

12. for Loop for <varName> in <list of words>;do <statements>; done; Example: for i in `cat list`; do cp "$i" "$i.bak;" done Example: for i in $PATHNAME/*; do rm $PATHNAME; done Example: >for x in *; do echo $x; done Note: the last example is directly from the command line

13. Calculate the average in a script #!/bin/bash if [ $# -lt 1 ]; then echo "usage: at least one argument needed" exit 1 fi value=0 count=0 for i in $@ do value=$[$value+$i] count=$[$count+1] done average=$((value/count)) echo $average average 1 outputs 1 average 1 2 3 outputs 2

14. Script Functions <funcName>() { <cmdList> } Example: doSomething doSomething() { ls –l | more; } doSomething Note:Function must be declared before it can be used. Note:Spaces required before and after braces Note: A common error is forgetting the required spaces

15. Functions with arguments • Arguments • $@ means all arguments • $* means all arguments, but treats quoted argments as one with embedded spaces • $0 is the command name • $1 first argument • $2 second argument • $# number of arguments • Example: LL() { ls –lR $@ | more; } LL / • Example: mycd() { cd $@; pwd; }

16. Shell Startups .bash_profile and .bashrc in a user’s home directory • .bash_profile • configures the login environment • Most .bash_profiles also execute .bashrc • .bashrc: configures subshell environments • To customize a users environment, normally edit .bashrc • include • Include aliases, variables, functions, search path ($PATH) • Good idea: Make the script in a test file first • Takes effect when logging in or executiong the source command