diff options
| -rw-r--r-- | bash.html.markdown | 64 |
1 files changed, 58 insertions, 6 deletions
diff --git a/bash.html.markdown b/bash.html.markdown index 708131bd..4d80545e 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -4,6 +4,7 @@ tool: bash contributors: - ["Max Yankov", "https://github.com/golergka"] - ["Darren Lin", "https://github.com/CogBear"] + - ["Alexandre Medeiros", "http://alemedeiros.sdf.org"] filename: LearnBash.sh --- @@ -35,8 +36,22 @@ VARIABLE = "Some string" # Using the variable: echo $VARIABLE echo "$VARIABLE" +echo '$VARIABLE' # When you use the variable itself — assign it, export it, or else — you write # its name without $. If you want to use variable's value, you should use $. +# Note that ' (single quote) won't expand the variables! + +# String substitution in variables +echo ${VARIABLE/Some/A} +# This will substitute the first occurance of "Some" with "A" + +# Bultin variables: +# There are some useful builtin variables, like +echo "Last program return value: $?" +echo "Script's PID: $$" +echo "Number of arguments: $#" +echo "Scripts arguments: $@" +echo "Scripts arguments separeted in different variables: $1 $2..." # Reading a value from input: echo "What's your name?" @@ -44,13 +59,18 @@ read NAME # Note that we didn't need to declare new variable echo Hello, $NAME! # We have the usual if structure: -if true +# use 'man test' for more info about conditionals +if [ $NAME -ne $USER ] then - echo "This is expected" + echo "Your name is you username" else - echo "And this is not" + echo "Your name isn't you username" fi +# There is also conditional execution +echo "Always executed" || echo "Only executed if first command fail" +echo "Always executed" && echo "Only executed if first command does NOT fail" + # Expressions are denoted with the following format: echo $(( 10 + 5 )) @@ -67,6 +87,13 @@ ls -l # Lists every file and directory on a separate line # txt files in the current directory: ls -l | grep "\.txt" +# You can also redirect a command output, input and error output. +python2 hello.py < "input.in" +python2 hello.py > "output.out" +python2 hello.py 2> "error.err" +# The output error will overwrite the file if it exists, if you want to +# concatenate them, use ">>" instead. + # Commands can be substitued within other commands using $( ): # The following command displays the number of files and directories in the # current directory. @@ -80,11 +107,36 @@ case "$VARIABLE" in *) 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 +# For loops iterate for as many arguments given: +# The contents of var $VARIABLE is printed three times. +# Note that ` ` is equivalent to $( ) and that seq returns a sequence of size 3. +for VARIABLE in `seq 3` do echo "$VARIABLE" done +# You can also define functions +# Definition: +foo () +{ + echo "Arguments work just like script arguments: $@" + echo "And: $1 $2..." + echo "This is a function" + return 0 +} + +# Calling your function +foo "My name is" $NAME + +# There are a lot of useful commands you should learn: +tail -n 10 file.txt +# prints last 10 lines of file.txt +head -n 10 file.txt +# prints first 10 lines of file.txt +sort file.txt +# sort file.txt's lines +uniq -d file.txt +# report or omit repeated lines, with -d it reports them +cut -d ',' -f 1 file.txt +# prints only the first column before the ',' character ``` |