Switch Case in Bash¶

The case statement itself does not directly support regex.
It uses glob patterns for matching.

Syntax¶

Basic syntax of switch case in bash:

case <value> in  
    <pattern>)  
        <command>;  
        ;;  
    (<pattern>|<other_pattern>)  
        <command>;  
        ;;  
    *)  
        printf "Default case\n";  
        ;;  
esac

case <value> in is the beginning of the switch case.

The value is the value that will be compared to the patterns.
This is typically a variable, but can be any value.
- E.g.:
```
case $1 in  
```

Each case starts with a pattern, which is a value or range of values.

The patterns can be either surrounded in parentheses (), or just ended
with a closing parenthesis ).
Multiple patterns can be given for one case, separated by |.
- E.g.:
```
case $1 in  
    (1*|2*|3*)  
        echo "Starts with 1, 2 or 3";  
        ;;  
```
- This can also be done by using a set ([ ]):
```
case $1 in  
    ([123]*)  
        echo "Starts with 1, 2 or 3";  
        ;;  
```
- The above cases will match any value that starts with 1, 2 or 3.
- The * is a wildcard, which matches any character (see Pattern Matching in man bash).
Each command in a case is ended by a semicolon ;.
Each case is ended by two semicolons ;; and a newline.

The default case is defined with *), and is optional.

Globbing and Regex in Patterns¶

The pattern matching is different from regex you'd normally use in Bash.
You can use globbing in patterns.
It's Bash's pattern matching (see Pattern Matching in man bash).

Example:

#!/bin/bash  

input="example.txt"  

case "$input" in  
  *.txt)  
    echo "It's a text file."  
    ;;  
  *.jpg|*.png)  
    echo "It's an image file."  
    ;;  
  *)  
    echo "File type is unknown."  
    ;;  
esac

Pattern Matching Operators¶

Operator	Description
`*`	Matches any string, including the null string. (see note)
`?`	Matches any single character.
`[...]`	Matches any one of the enclosed characters.

A note about `*` in patterns:¶

When the globstar shell option is enabled, and * is used in
a pathname expansion, two *s (**) used as a single pattern will
match all files recursively, and zero or more directories and subdirectories.

Extended Pattern Matching Operators¶

Note: This requires the extglob option to be enabled with shopt -s extglob.
When extended pattern matching becomes available, you have access to more types of operators:

?(pattern-list)
- Matches zero or one occurrence of the given patterns
*(pattern-list)
- Matches zero or more occurrences of the given patterns
+(pattern-list)
- Matches one or more occurrences of the given patterns
@(pattern-list)
- Matches one of the given patterns
!(pattern-list)
- Matches anything except one of the given patterns

Operator	Description
`?(pattern-list)`	Matches zero or one occurrence of the given patterns
`*(pattern-list)`	Matches zero or more occurrences of the given patterns
`+(pattern-list)`	Matches one or more occurrences of the given patterns
`@(pattern-list)`	Matches one of the given patterns
`!(pattern-list)`	Matches anything except one of the given patterns

Tips and Tricks¶

Converting the value to lowercase temporarily can make things easier:

# Just change the value to lowercase temporarily  
case ${name,,} in

Note: This method of string manipulation (parameter expansion) is not POSIX-compliant.

A POSIX-compliant way to do this:

lname=$(printf "%s" "$name" | tr '[:upper:]' '[:lower:]')  
case $lname in