Bash string manipulation

#bash #string #manipulation #systemcommands

In bash, there are several string manipulation operations that can be used to remove parts of a string based on patterns. Here are some of the most commonly used ones

${variable#pattern}:
- Removes the shortest match of pattern from the beginning of variable.

   x="abc.def.ghi"
   echo ${x#*.}  # Outputs: def.ghi

${variable##pattern}:
- Removes the longest match of pattern from the beginning of variable.

   x="abc.def.ghi"
   echo ${x##*.}  # Outputs: ghi

${variable%pattern}:
- Removes the shortest match of pattern from the end of variable.

   x="abc.def.ghi"
   echo ${x%.*}  # Outputs: abc.def

${variable%%pattern}:
- Removes the longest match of pattern from the end of variable.

   x="abc.def.ghi"
   echo ${x%%.*}  # Outputs: abc

${variable:offset:length}:
- Extracts a substring from variable starting at offset and of length length.

   x="abc.def.ghi"
   echo ${x:4:3}  # Outputs: def

${variable/pattern/replacement}:
- Replaces the first match of pattern with replacement in variable.

   x="abc.def.ghi"
   echo ${x/def/xyz}  # Outputs: abc.xyz.ghi

${variable//pattern/replacement}:
- Replaces all matches of pattern with replacement in variable.

   x="abc.def.ghi"
   echo ${x//./-}  # Outputs: abc-def-ghi

${variable^pattern}:
- Converts the first character to uppercase (bash 4.0 and above).

   x="abc"
   echo ${x^}  # Outputs: Abc

${variable^^pattern}:
- Converts all characters to uppercase (bash 4.0 and above).

   x="abc"
   echo ${x^^}  # Outputs: ABC

${variable,pattern}:
- Converts the first character to lowercase (bash 4.0 and above).
```
x="ABC"
echo ${x,}  # Outputs: aBC
```
${variable,,pattern}:
- Converts all characters to lowercase (bash 4.0 and above).
```
x="ABC"
echo ${x,,}  # Outputs: abc
```