Revision [539]
This is an old revision of HowToConditional made by DavidLee on 2009-05-21 18:58:21.
How To test a condition
Conditions can be tested with either the boolean operations "
" and "&&" or with the the if/elif/else/then clauses.Boolean OperationsIf you only need execute a single command or a small block then boolean operations are the easiest way for example if "command" returns successfully then print "is success" $ command && echo is success If the file "myfile.txt" exists then read the first line from the file and print it. $ [ -e myfile.txt ] && { read VAR < myfile.txt ; echo $VAR ; }Structured Conditionals (if / elif / else / fi )If the condition or conditional operations are more complicated then the structured conditionals are more useful. This is the if / elif / else / fi construct. The general form is if condition1 ; then condition1 commands elif condition2 ; then condition2 commands else otherwise commands fi |
