Bash scripting Tutorial> PDF DOWNLOAD< > PDF DOWNLOAD< This bash script tutorial assumes no previous knowledge of bash scripting. As you will soon discover in this quick comprehensive bash scripting guide, learning the bash shell scripting is very easy task. However, if you do not find an answer to your questions by reading this bash tutorial or you need extra help, feel free to ask us on our new Linux Forum. Advanced Bash-Scripting Guide. Using read with file redirection 15-8. Problems reading. Using getopts to read the options/arguments passed to a script 15-22. 'Including' a data file 15-23. A (useless) script that. We will be more than happy to help you with your bash questions there. Lets begin this bash scripting tutorial with a simple "Hello World" script. Let's start with Learning the bash Shell: Unix Shell Programming Bash Scripting Beginners Guide FREE PDF DOWNLOAD Bash Scripting Advanced Guide FREE PDF DOWNLOAD 1. Hello World Bash Shell Script. First you need to find out where is your bash interpreter located. Enter the following into your command line: $ which bash. Open up you favorite text editor and a create file called hello_world. Insert the following lines to a file: NOTE: Every bash shell script in this tutorial starts with shebang: "#!" which is not read as a comment. First line is also a place where you put your interpreter which is in this case: /bin/bash. Here is our first bash shell script example: #!/bin/bash# declare STRING variable. STRING="Hello World"#print variable on a screenecho $STRINGNavigate to a directory where your hello_world. Now you are ready to execute your first bash script: 2. Simple Backup bash shell script#!/bin/bashtar - czf myhome_directory. Variables. In this example we declare simple bash variable and print it on the screen ( stdout ) with echo command.#!/bin/bash. STRING="HELLO WORLD!!!"echo $STRING Your backup script and variables: #!/bin/bash. This bash script tutorial assumes no previous knowledge of bash scripting.As you will soon discover in this quick. Read file into bash array #!/bin/bash. linuxconfig.org $ cat bash.txt Bash Scripting Tutorial. Bash script to read a file. Not sure why the last line does not cut the ' from the script: #!/bin/bash FILENAME=$1 while read line do cut -d ''' -f2 echo $line done. about us tour help blog chat data legal privacy. Data extraction from a text file using bash. I want to extract the data as follow. Writing a bash script to read a text file of numbers into arrays, by column. #!/bin/bash while IFS='' read -r line || [[ -n. You will not be given a chance to enter data manually. – carpie Jan. we open the file descriptor 3 for the file passed as the script argument and tell read to use this. Apparently, the title and the body of the question did not seem quite the same to me. Here are two solutions: Importing data from an external file into a Bash script: Read the file and store its contents as entries in an array. OF=myhome_directory_$(date +%Y%m%d). OF /home/linuxconfig 3. Global vs. Local variables#!/bin/bash#Define bash global variable#This variable is global and can be used anywhere in this bash script. VAR="global variable"function bash {#Define bash local variable#This variable is local to bash function onlylocal VAR="local variable"echo $VAR}echo $VARbash# Note the bash global variable did not change# "local" is bash reserved wordecho $VAR4. Passing arguments to the bash script#!/bin/bash# use predefined variables to access passed arguments#echo arguments to the shellecho $1 $2 $3 ' - > echo $1 $2 $3'# We can also store arguments from bash command line in special arrayargs=("$@")#echo arguments to the shellecho ${args[0]} ${args[1]} ${args[2]} ' - > args=("$@"); echo ${args[0]} ${args[1]} ${args[2]}'#use $@ to print out all arguments at onceecho $@ ' - > echo $@'# use $# variable to print out# number of arguments passed to the bash scriptecho Number of arguments passed: $# ' - > echo Number of arguments passed: $#' /arguments. Bash Scripting Tutorial 5. Executing shell commands with bash#!/bin/bash# use backticks " ` ` " to execute shell commandecho `uname - o`# executing bash command without backticksecho uname - o 6. Reading User Input#!/bin/bashecho - e "Hi, please type the word: \c "read wordecho "The word you entered is: $word"echo - e "Can you please enter two words? Here is your input: \"$word. How do you feel about bash scripting? REPLYreadecho "You said $REPLY, I'm glad to hear that! What are your favorite colours ? My favorite colours are also ${colours[0]}, ${colours[1]} and ${colours[2]}: -)" 7. Bash Trap Command#!/bin/bash# bash trap commandtrap bashtrap INT# bash clear screen commandclear; # bash trap function is executed when CTRL- C is pressed: # bash prints message => Executing bash trap subrutine ! CTRL+C Detected !. Exit." sleep 1; doneecho "Exit Bash Trap Example!!!" 8. Arrays. Declare simple bash array#!/bin/bash#Declare array with 4 elements. Catching user input. 8.2. Michel's files. You can solve this problem using special access modes on the script file, see SUID and SGID in the. michel ~/testdir> cat sysnotes.sh #!/bin/bash # This script makes an index of. ARRAY=( 'Debian Linux' 'Redhat Linux' Ubuntu Linux )# get number of elements in the array. ELEMENTS=${#ARRAY[@]}# echo each element in array # for loopfor (( i=0; i< $ELEMENTS; i++)); doecho ${ARRAY[${i}]}done 8. Read file into bash array#!/bin/bash# Declare arraydeclare - a ARRAY# Link filedescriptor 1. LINE; do. ARRAY[$count]=$LINE((count++))doneecho Number of elements: ${#ARRAY[@]}# echo array's contentecho ${ARRAY[@]}# restore stdin from filedescriptor 1. Bash script execution with an output: linuxconfig. Bash. Scripting. Tutorial. Guidelinuxconfig. Number of elements: 4. Bash Scripting Tutorial Guidelinuxconfig. Bash if / else / fi statements. Simple Bash if/else statement. Please note the spacing inside the [ and ] brackets! Without the spaces, it won't work!#!/bin/bashdirectory="./Bash. Scripting"# bash check if directory existsif [ - d $directory ]; thenecho "Directory exists"else echo "Directory does not exists"fi 9. Nested if/else#!/bin/bash# Declare variable choice and assign value 4choice=4# Print to stdoutecho "1. Bash"echo "2. Scripting"echo "3. Tutorial"echo - n "Please choose a word [1,2 or 3]? Loop while the variable choice is equal 4# bash while loopwhile [ $choice - eq 4 ]; do# read user inputread choice# bash nested if/elseif [ $choice - eq 1 ] ; thenecho "You have chosen word: Bash"else if [ $choice - eq 2 ] ; thenecho "You have chosen word: Scripting"elseif [ $choice - eq 3 ] ; thenecho "You have chosen word: Tutorial"elseecho "Please make a choice between 1- 3 !"echo "1. Bash"echo "2. Scripting"echo "3. Tutorial"echo - n "Please choose a word [1,2 or 3]? Bash Comparisons. Arithmetic Comparisons- lt< -gt> -le< =- ge> =- eq==- ne!=#!/bin/bash# declare integers. NUM1=2. NUM2=2if [ $NUM1 - eq $NUM2 ]; thenecho "Both Values are equal"else echo "Values are NOT equal"fi #!/bin/bash# declare integers. NUM1=2. NUM2=1if [ $NUM1 - eq $NUM2 ]; thenecho "Both Values are equal"else echo "Values are NOT equal"fi #!/bin/bash# declare integers. NUM1=2. NUM2=1if [ $NUM1 - eq $NUM2 ]; thenecho "Both Values are equal"elif [ $NUM1 - gt $NUM2 ]; thenecho "NUM1 is greater then NUM2"else echo "NUM2 is greater then NUM1"fi 1. String Comparisons=equal!=not equal< less then> greater then- n s. Declare string S1. S1="Bash"#Declare string S2. S2="Scripting"if [ $S1 = $S2 ]; thenecho "Both Strings are equal"else echo "Strings are NOT equal"fi #!/bin/bash#Declare string S1. S1="Bash"#Declare string S2. S2="Bash"if [ $S1 = $S2 ]; thenecho "Both Strings are equal"else echo "Strings are NOT equal"fi 1. Bash File Testing- b filename. Block special file- c filename. Special character file- d directoryname. Check for directory existence- e filename. Check for file existence- f filename. Check for regular file existence not a directory- G filename. Check if file exists and is owned by effective group ID.- g filenametrue if file exists and is set- group- id.- k filename. Sticky bit- L filename. Symbolic link- O filename. True if file exists and is owned by the effective user id.- r filename. Check if file is a readable- S filename. Check if file is socket- s filename. Check if file is nonzero size- u filename. Check if file set- ser- id bit is set- w filename. Check if file is writable- x filename. Check if file is executable#!/bin/bashfile="./file"if [ - e $file ]; thenecho "File exists"else echo "File does not exists"fi Similarly for example we can use while loop to check if file does not exists. This script will sleep until file does exists. Note bash negator "!" which negates the - e option.#!/bin/bashwhile [ ! Sleep until file does exists/is createdsleep 1done 1. Loops. 12. 1. Bash for loop#!/bin/bash# bash for loopfor f in $( ls /var/ ); doecho $fdone Running for loop from bash shell command line: $ for f in $( ls /var/ ); do echo $f; done 1. Bash while loop#!/bin/bash. COUNT=6# bash while loopwhile [ $COUNT - gt 0 ]; doecho Value of count is: $COUNTlet COUNT=COUNT- 1done 1. Bash until loop#!/bin/bash. COUNT=0# bash until loopuntil [ $COUNT - gt 5 ]; doecho Value of count is: $COUNTlet COUNT=COUNT+1done 1. Control bash loop with. Here is a example of while loop controlled by standard input. Until the redirection chain from STDOUT to STDIN to the read command exists the while loop continues.#!/bin/bash# This bash script will locate and replace spaces# in the filenames. DIR="."# Controlling a loop with bash read command by redirecting STDOUT as# a STDIN to while loop# find will not truncate filenames containing spacesfind $DIR - type f | while read file; do# using POSIX class [: space: ] to find space in the filenameif [[ "$file" = *[[: space: ]]* ]]; then# substitute space with "_" character and consequently rename the filemv "$file" `echo $file | tr ' ' '_'`fi; # end of while loopdone 1. Bash Functions!/bin/bash# BASH FUNCTIONS CAN BE DECLARED IN ANY ORDERfunction function_B {echo Function B.}function function_A {echo $1}function function_D {echo Function D.}function function_C {echo $1}# FUNCTION CALLS# Pass parameter to function Afunction_A "Function A."function_B# Pass parameter to function Cfunction_C "Function C."function_D 1. Bash Select#!/bin/bash. PS3='Choose one word: ' # bash selectselect word in "linux" "bash" "scripting" "tutorial" doecho "The word you have selected is: $word"# Break, otherwise endless loopbreak doneexit 0 1. Case statement conditional#!/bin/bashecho "What is your preferred programming / scripting language"echo "1) bash"echo "2) perl"echo "3) phyton"echo "4) c++"echo "5) I do not know !"read case; #simple case bash structure# note in this case $case is variable and does not have to# be named case this is just an examplecase $case in. You selected bash"; ;2) echo "You selected perl"; ;3) echo "You selected phyton"; ;4) echo "You selected c++"; ;5) exitesac 1. Bash quotes and quotations. Quotations and quotes are important part of bash and bash scripting. Here are some bash quotes and quotations basics. Before we start with quotes and quotations we should know something about escaping meta characters. Escaping will suppress a special meaning of meta characters and therefore meta characters will be read by bash literally. To do this we need to use backslash "\" character. Example: #!/bin/bash#Declare bash string variable.
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