View Source: ManipulatingStrings - Waikato Linux Users Group

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!Two Methods For Finding The Length Of a String

*test="This is a string"

Method 1)

*echo ${#test}

Method 2)

*expr length test

Both will give you the correct length of 16.


!How can I get a substring of a variable?

Say the variable test contains the string "corndog" but we want just the "dog" part.

echo ${test:4:3} will return just "dog"

The 4 tells us the index of the char that will be the first char in the substring. The 3 tells us how many letters to add starting at the index.

!Remove Substrings (uses bash's pattern matching)

Strips *shortest* match of $substring from *front* of $string.
*${string#substring}

For example if $string contained "This is a string" and we replaced substring with ''T*'' an echo would result in
''his is a string''



Strips *longest* match of $substring from *front* of $string.
*${string##substring}

For example if $string contained "This is a string" and we replaced substring with ''T*'' an echo would result in an empty string. (The longest match was the entire string).



Strips *shortest* match of $substring from *back* of $string.
*${string%substring}

For example if $string contained "This is a string" and we replaced substring with ''s*'' an echo would result in
''This is a''



Strips *longest* match of $substring from *back* of $string.
*${string%%substring}

For example if $string contained "This is a string" and we replaced substring with ''s*'' an echo would result in
''Thi''   (The longest match)


!Concatenate variables.

*echo ${string1}${string2}

If we did:

*echo $string1string2

then bash would be looking for a variable called ''string1string2'' (which does not exist). This is why the curly brackets are necessary.

Another Example:

*echo ${string1}"Some more Text"

!Brace Expansion

*echo C{a,u,o}t

Will return ''Cat Cut Cot''

Another example of where this could be useful:

*mkdir ~~/test/{cat,dog,rabbit}

This will create a ''cat'' , ''dog'' and ''rabbit'' dir in ~~/test/

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Last edited on Monday, December 11, 2006 5:24:42 pm by BenStaz

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