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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
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  • ${variable##pattern}:
    • Removes the longest match of pattern from the beginning of variable. 
 x="abc.def.ghi" echo ${x##*.} # Outputs: ghi
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  • ${variable%pattern}:
    • Removes the shortest match of pattern from the end of variable. 
 x="abc.def.ghi" echo ${x%.*} # Outputs: abc.def
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  • ${variable%%pattern}:
    • Removes the longest match of pattern from the end of variable. 
 x="abc.def.ghi" echo ${x%%.*} # Outputs: abc
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  • ${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
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  • ${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
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  • ${variable//pattern/replacement}:
    • Replaces all matches of pattern with replacement in variable. 
 x="abc.def.ghi" echo ${x//./-} # Outputs: abc-def-ghi
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  • ${variable^pattern}:
    • Converts the first character to uppercase (bash 4.0 and above). 
 x="abc" echo ${x^} # Outputs: Abc
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  • ${variable^^pattern}:
    • Converts all characters to uppercase (bash 4.0 and above). 
 x="abc" echo ${x^^} # Outputs: ABC
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  • ${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.

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