Bash Shell Scripting Workshop

Transcript

1. Bash Scripting Prepared by Ahmed Magdy Ezzeldin

2. File System • / is not allowed in a file

   name • file extensions are not important • File and folder names are case sensitive • Names containing spaces are escaped by \ or "" • Hidden files start with . • Current directory alias . and parent directory alias .. • ls, ls -a, ls -l, cp, mv, rm, rm -rdf, ln, ln -sf

3. Variable and Strings • Strings are enclosed in “” ''

   or just written with spaces escaped by \ VAR=”How are you” VAR='How are you' VAR=HOW\ are\ you • Variables $VAR ${VAR} # e.g. ${FILE}.txt echo “my name is $NAME” echo “my name is “$NAME read VAR read VAR1 VAR2

4. Math • echo $((1+1)) • echo $[1+1] • echo `expr

   1 + 1` • A=$((B*C)) • let A+=1 • echo "3.4+7/8-(5.94*3.14)" | bc

5. File Ownership and Permissions • Group and Ownership chown, chgrp,

   ls -l chown user:group file sudo chown • Permissions of files and directories chmod 755 file chmod +x file chmod -x file (r)ead (w)rite e(x)ecute 4 2 1

6. Users, su, sudo • su, sudo, visudo, /etc/sudoers, su user

   • sudo bash • /etc/passwd • ~/

7. Processes and Subshells • ps, pgrep, top, jobs, fg, &,

   kill, signals • Sub-shells from : • Loops • $() • Back ticks `` • bash command • /proc • fuser

8. Loops • While loop while read VAR; do echo $VAR;

   done • For each loop for VAR in {1..5}; do echo $VAR; done for VAR in 1 2 3 4 5; do echo $VAR; done for VAR in {0..10..2}; do echo $VAR; done for VAR in $(seq 0 2 10); do echo $VAR; done • For loop with counter for (( i=0; i<=10; i+=2 )); do echo $i; done

9. if and switch case • If then, else, elif, fi

   if [ -d $F ]; then rm -rdf $F elif [ -f $F ]; then rm $F else echo “Unknown file type” fi • case, esac while read l; do case $l in 1) echo "One";; 2) echo "Two";; 3) echo "Three";; *) echo "Invalid"; break;; esac done

10. I/O Redirection • >, >>, <, &>, 2&>, 2>, |

    echo “error” 1>&2 # redirect std_output to std_err some_error_producing_command 2>&1 some_command &>> log_file_errors_and_output some_command >> log_file_output_only some_command 2>> log_file_errors_only command | filter_command command < file command > file # truncates and writes into file command1 2>&1 | command2 command1 |& command2 • Mute by redirecting to /dev/null file

11. Named Pipes and Network and Signal Processing • Network exec

    9<>/dev/tcp/google.com/80 echo -e "GET / HTTP/1.0\n\n" >&9 while read line <&9; do echo $line; done • Named Pipes mkfifo pipe while read l; do echo $l; done < pipe echo “hi” > pipe # on another terminal window • Signal Processing #!/bin/bash function handle_signal () { echo "Hi man I got the signal" } trap "handle_signal; exit" SIGINT sleep 100

12. Cool Stuff and GUI • Install these: libnotify-bin, zenity, festival

    • date '+%l oclock' | festival –tts • zenity --list --hide-header --text="Are you coming today?" --checklist --column "" --column "" FALSE "Yes" FALSE "No" FALSE "May be" • zenity --calendar --date-format="%Y/%m/%d" • zenity --text="Select Hour" --title="Select Hour" --scale --min-value=0 --max- value=24 --value=17 • zenity --text="Select Minutes" --title="Select Minutes" --scale --min-value=0 --max-value=59 --value=0 • zenity --info --text="Did you know this info" • zenity --error --text="There is an error" • zenity --entry | festival --tts • zenity --file-selection • <progres command> | zenity --progress --auto-close • notify-send -t 10 "hi man" "details"

13. Launchers • When you drag a file or folder onto

    a launcher it is sent as $1 to the launcher script

14. Example Codes • Bluetooth Obex-push NEW_FILE_NAME=`echo $1 | awk -vFS="/"

    '{print $NF;}'` ussp-push 00:22:65:89:22:E6@9 "$1" "$NEW_FILE_NAME" • Close the computer when your browser finishes downloading your_file while true; do sleep 5; if [ -z "`fuser ~/your_file`" ]; then break; fi; done; sudo init 0 • Tell me the time whenever I lock my screen or unlock it • Simple spider using curl and wget • Log your time easily and report to a Redmine service • Think of more ...

15. Thank you

16. References http://www.linuxcommand.org/lts0040.php http://www.cyberciti.biz/faq/bash-for-loop/ http://linuxcommand.org/wss0160.php http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-10.html http://wiki.bash-hackers.org/syntax/redirection http://www.kernel.org/doc/man-pages/online/pages/man5/proc.5.html