Difference between revisions of "Tutorial: A bit of Bash"
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=Displaying strings and various quantities= | =Displaying strings and various quantities= | ||
− | =Getting the length of a string variable= | + | ===Getting the length of a string variable=== |
name="toto.txt" | name="toto.txt" | ||
echo "length of $name = ${#name}" #will output 8 | echo "length of $name = ${#name}" #will output 8 | ||
− | =Getting extension and name (without extension) of a file= | + | ===Getting extension and name (without extension) of a file=== |
fullPath="/usr/local/bin/toto.txt" | fullPath="/usr/local/bin/toto.txt" |
Revision as of 12:18, 26 November 2013
--D. Thiebaut (talk) 11:03, 26 November 2013 (EST)
A quick review of some useful Bash commands that can be used on the command line, or that can be included in bash scripts
Contents
Creating a bash script
- first line should contain name of bash shell
#! /bin/bash
- make the script executable
chmod +x scriptname
Variables
- Declaration
file="hello.txt" file=`ls -1 *.txt | head -1` # get the first .txt file in the directory
- In expressions: put a $ in front of it!
URL="http://cs.smith.edu/dftwiki/images/" file="toto.png" pathFile=$URL$file file="alpha" pathFile=$URL${file}.png # add braces if string needs to be concatenated to variable
Script Parameters
- assume doit.sh is a script and it is called as follows:
doit.sh 8 2000 50
- To get the arguments inside the script:
NP=$1 # will get 8 N=$2 # will get 2000 M=$3 # will get 50
- To test if the number of parameters is 3 inside the script:
if [ "$#" -ne 3 ]; then echo "syntax: doit.sh NP N M" exit fi
Displaying strings and various quantities
Getting the length of a string variable
name="toto.txt" echo "length of $name = ${#name}" #will output 8
Getting extension and name (without extension) of a file
fullPath="/usr/local/bin/toto.txt" fileName="${fullPath##*/}" echo "file name with extension = $fileName" extension="${fullPath##*.}" fileName="${fileName%.*}" echo "fullPath = $fullPath" echo "fileName without extension = $fileName" echo "extension = $extension"