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Merge pull request #365 from alemedeiros/master
[bash/en] Improved bash file
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commit
262ea9c3ce
@ -4,6 +4,7 @@ tool: bash
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contributors:
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- ["Max Yankov", "https://github.com/golergka"]
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- ["Darren Lin", "https://github.com/CogBear"]
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- ["Alexandre Medeiros", "http://alemedeiros.sdf.org"]
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filename: LearnBash.sh
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---
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@ -35,8 +36,22 @@ VARIABLE = "Some string"
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# Using the variable:
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echo $VARIABLE
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echo "$VARIABLE"
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echo '$VARIABLE'
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# When you use the variable itself — assign it, export it, or else — you write
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# its name without $. If you want to use variable's value, you should use $.
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# Note that ' (single quote) won't expand the variables!
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# String substitution in variables
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echo ${VARIABLE/Some/A}
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# This will substitute the first occurance of "Some" with "A"
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# Bultin variables:
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# There are some useful builtin variables, like
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echo "Last program return value: $?"
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echo "Script's PID: $$"
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echo "Number of arguments: $#"
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echo "Scripts arguments: $@"
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echo "Scripts arguments separeted in different variables: $1 $2..."
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# Reading a value from input:
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echo "What's your name?"
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@ -44,13 +59,18 @@ read NAME # Note that we didn't need to declare new variable
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echo Hello, $NAME!
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# We have the usual if structure:
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if true
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# use 'man test' for more info about conditionals
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if [ $NAME -ne $USER ]
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then
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echo "This is expected"
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echo "Your name is you username"
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else
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echo "And this is not"
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echo "Your name isn't you username"
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fi
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# There is also conditional execution
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echo "Always executed" || echo "Only executed if first command fail"
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echo "Always executed" && echo "Only executed if first command does NOT fail"
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# Expressions are denoted with the following format:
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echo $(( 10 + 5 ))
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@ -67,6 +87,13 @@ ls -l # Lists every file and directory on a separate line
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# txt files in the current directory:
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ls -l | grep "\.txt"
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# You can also redirect a command output, input and error output.
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python2 hello.py < "input.in"
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python2 hello.py > "output.out"
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python2 hello.py 2> "error.err"
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# The output error will overwrite the file if it exists, if you want to
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# concatenate them, use ">>" instead.
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# Commands can be substitued within other commands using $( ):
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# The following command displays the number of files and directories in the
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# current directory.
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@ -80,11 +107,36 @@ case "$VARIABLE" in
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*) echo "It is not null.";;
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esac
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#For loops iterate for as many arguments given:
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#The contents of var $VARIABLE is printed three times.
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for VARIABLE in x y z
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# For loops iterate for as many arguments given:
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# The contents of var $VARIABLE is printed three times.
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# Note that ` ` is equivalent to $( ) and that seq returns a sequence of size 3.
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for VARIABLE in `seq 3`
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do
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echo "$VARIABLE"
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done
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# You can also define functions
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# Definition:
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foo ()
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{
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echo "Arguments work just like script arguments: $@"
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echo "And: $1 $2..."
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echo "This is a function"
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return 0
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}
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# Calling your function
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foo "My name is" $NAME
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# There are a lot of useful commands you should learn:
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tail -n 10 file.txt
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# prints last 10 lines of file.txt
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head -n 10 file.txt
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# prints first 10 lines of file.txt
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sort file.txt
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# sort file.txt's lines
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uniq -d file.txt
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# report or omit repeated lines, with -d it reports them
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cut -d ',' -f 1 file.txt
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# prints only the first column before the ',' character
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```
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