diff options
Diffstat (limited to 'bash.html.markdown')
| -rw-r--r-- | bash.html.markdown | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/bash.html.markdown b/bash.html.markdown index cb805da7..8c40931e 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -16,6 +16,7 @@ contributors: - ["Betsy Lorton", "https://github.com/schbetsy"] - ["John Detter", "https://github.com/jdetter"] - ["Harry Mumford-Turner", "https://github.com/harrymt"] + - ["Martin Nicholson", "https://github.com/mn113"] filename: LearnBash.sh --- @@ -74,8 +75,13 @@ echo ${Variable/Some/A} # => A string # Substring from a variable Length=7 -echo ${Variable:0:$Length} # => Some st +echo ${Variable:0:Length} # => Some st # This will return only the first 7 characters of the value +echo ${Variable: -5} # => tring +# This will return the last 5 characters (note the space before -5) + +# String length +echo ${#Variable} # => 11 # Default value for variable echo ${Foo:-"DefaultValueIfFooIsMissingOrEmpty"} @@ -174,6 +180,16 @@ then echo "This will run if $Name is Daniya OR Zach." fi +# There is also the =~ operator, which tests a string against a Regex pattern: +Email=me@example.com +if [[ "$Email" =~ [a-z]+@[a-z]{2,}\.(com|net|org) ]] +then + echo "Valid email!" +fi +# Note that =~ only works within double [[ ]] square brackets, +# which are subtly different from single [ ]. +# See http://www.gnu.org/software/bash/manual/bashref.html#Conditional-Constructs for more on this. + # Redefine command 'ping' as alias to send only 5 packets alias ping='ping -c 5' # Escape alias and use command with this name instead @@ -228,10 +244,13 @@ mv s0urc3.txt dst.txt # sorry, l33t hackers... # Since bash works in the context of a current directory, you might want to # run your command in some other directory. We have cd for changing location: cd ~ # change to home directory +cd # also goes to home directory cd .. # go up one directory # (^^say, from /home/username/Downloads to /home/username) cd /home/username/Documents # change to specified directory cd ~/Documents/.. # still in home directory..isn't it?? +cd - # change to last directory +# => /home/username/Documents # Use subshells to work across directories (echo "First, I'm here: $PWD") && (cd someDir; echo "Then, I'm here: $PWD") @@ -256,6 +275,7 @@ print("#stderr", file=sys.stderr) for line in sys.stdin: print(line, file=sys.stdout) EOF +# Variables will be expanded if the first "EOF" is not quoted # Run the hello.py Python script with various stdin, stdout, and # stderr redirections: |