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diff --git a/bash.html.markdown b/bash.html.markdown new file mode 100644 index 00000000..8cf7be18 --- /dev/null +++ b/bash.html.markdown @@ -0,0 +1,84 @@ +--- + +language: bash +contributors: + - ["Max Yankov", "https://github.com/golergka" - "Darren Lin", "https://github.com/CogBear"] +filename: LearnBash.sh + +--- + +Bash is a name of the unix shell, which was also distributed as the shell for the GNU operating system and as default shell on Linux and Mac OS X. +Nearly all examples below can be a part of a shell script or executed directly in the shell. + +[Read more here.](http://www.gnu.org/software/bash/manual/bashref.html) + +```bash +#!/bin/sh +# First line of the script is shebang which tells the system how to execute the script: http://en.wikipedia.org/wiki/Shebang_(Unix) +# As you already figured, comments start with #. Shebang is also a comment. + +# Simple hello world example: +echo Hello, world! + +# Each command starts on a new line, or after semicolon: +echo 'This is the first line'; echo 'This is the second line' + +# Declaring a variable looks like this: +VARIABLE="Some string" + +# But not like this: +VARIABLE = "Some string" # Bash will decide that VARIABLE is a command he must execute and give an error because it couldn't be found. + +# Using the variable: +echo $VARIABLE +echo "$VARIABLE" +# When you use the variable itself — assign it, export it, or else — you write it's name without $. If you want to use variable's value, you should use $. + +# Reading a value from input: +echo "What's your name?" +read NAME # Note that we didn't need to declare new variable +echo Hello, $NAME! + +# We have the usual if structure: +if true +then + echo "This is expected" +else + echo "And this is not" +fi + +# Expressions are denoted with the following format: +echo $(( 10 + 5 )) + +# Unlike other programming languages, bash is a shell — so it works in a context of current directory. +# You can list files and directories in the current directories with ls command: +ls + +# These commands have options that control their execution: +ls -l # Lists every file and directory on a separate line + +# Results of the previous command can be passed to the next command as input. +# grep command filters the input with provided patterns. That's how we can list txt files in the current directory: +ls -l | grep "\.txt" + +# Commands can be substitued within other commands using $( ): +# The following command displays the number of files and directories in the current directory. +echo "There are $(ls | wc -l) items here." + +#Bash uses a case statement that works similarily to switch in Java and C++: +case "$VARIABLE" +in + #List patterns for the conditions you want to meet + 0) echo "There is a zero." + 1) echo "There is a one." + *) echo "It is not null." +esac + +#For loops iterate for as many arguments given: +#The contents of var $VARIABLE is printed three times. +for $VARIABLE in x y z +do + echo "$VARIABLE" +done + +``` |