Bash string manipulation

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
  

These operations provide a powerful and flexible way to manipulate strings directly within bash scripts, allowing for efficient and concise code.