shell programming branch of the case statement

shell programming branch of the case statement

case and if the multi-branch statement branch statement is very similar.

if multiple branching statements generally used where there is (the interval range); for example: 0-100.

if necessary to determine a plurality of different conditions.

If a case statement branches to a fixed value which matches; or in the presence of multiple values ​​of a variable, required command sequence performs different value for each of them.

Analyzing case but different values ​​of a variable.

case model:

Implementation process:

First, using the "variable value" is compared with the pattern 1, if the value identical to Run Mode 1 1 sequence, until she met ";;" esac after jumping to the end.

If the pattern does not match the 1, 2 continue compared with the next mode, if the same sequence of mode 2 Run 2, met know ";;" to jump to the end esac. If you still can not find any matching value, then the implementation of "*)" the default mode after the default command sequence, until she met the end of esac.

When using the case branching statements, there are a few points to note:

Tail 1.case word line must be 'in', each pattern must end with a right parenthesis ')'.

2. Double semicolons ";;", indicating the end of a command sequence.

3. The pattern string, can use the "[]" represents a continuous range, such as: [0-9]; symbols can also use the vertical bar "|" (or represented), such as: a | b.

4. Final " )" denotes the default mode, in which " " corresponds to a wildcard.