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Cursor movements in command line
emacs mode:
| <Esc> . |
...
| repeat last word of previous command |
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| Ctrl-a |
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| jump to beginning of line |
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| Ctrl-e |
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| jump to end of line |
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| Ctrl-r |
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| search backwards in command history | |
| Ctrl-c |
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| interrupt current command/process |
Control structures
if then else
| Volet |
|---|
| if |
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| expression_1; then Statement(s) to be executed if expression 1 is true [elif expression_2; then Statement(s) to be executed if expression 2 is true elif expression_3; then Statement(s) to be executed if expression 3 is true else Statement(s) to be executed if no expression is true] fi |
'elifexpression ; then' and 'else' are optional!!!expressions can look like this
Example 'expressions':
Arithmetic expression examples ( a=2 ):
(( a == 3 ))
(( b != 3 ))
(( $a >= 3 ))
In Arithmetic expressions '(( ... ))' it is not necessary to put the '$' infront in front of variables since strings are not allowed so all strings are assumed to be variables anyways.
String expressions examples ( abc="Bonjour" ):
equal:
[[ "$abc" == "Hello" ]]
not equal:
[[ "$abc" != "Hello" ]]
The more common but less recomended recommended way is:
[ $a -le 3 ]
resp.
[ "$abc" -nq "Hello" ]
Note: It is mandatory to keep a 'space' just before and after the double and single square brackets!!!
and: &&
or: ||
If you want to know more about the comparison operators try:
$ man test
or
$ man bash -> CONDITIONAL EXPRESSIONS
case-statement
| Volet |
|---|
| case test_string in pattern_1) statement(s) ;; pattern_2) statement(s) ;; *) default_statement(s) ;; esac |
Examples:
mon="Jan"
case "$mon" in
"Jan") echo January
month=January ;;
"Feb") echo February
month=February ;;
*) echo "month not known" ;;
esac
# Determine number of days per month
case ${month} in
04|06|09|11) days=30 ;;
02) if (( year % 4 == 0 )) && \
( (( year % 100 != 0 )) || (( year % 400 == 0 )) ) ; then
days=29
else
days=28
fi ;;
*) days=31 ;;
esac
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