Using grep search with array containing strings and spaces
 

Hi Everyone,

I want to be able to create an array that contains both strings and spaces within each element and use it as the pattern that grep will search for within a file.

I know that I can do it if I explicitly type the string within the grep command.

grep -ciw 'Hello world' file.txt

But it doesn't seem to work when I place the string with spaces in an array.

array[1]="'Hello'"
array[2]="'Hello world'"

grep -ciw "${array[1]} file.txt
grep -ciw "${array[2]} file.txt

grep for array[1] works, but the value for array[2] does not.

I tried all the possible premutation with regular expression to get it to work, with no luck.

Ultimately, I want to know if you can place single qoutes and or regular expressions within an array and have grep use it as a regular expression and not a literal value.

Any help would be appreciated...Thanks!!!

Hi,

try without the single-quotes:
array[2]="Hello world"

Invoke it with double-quotes:
grep -ciw "${array[2]}" file.txt

In scripting it's vital to understand how the shell handles arguments and whitespace. Read these three pages carefully:

http://mywiki.wooledge.org/Arguments
http://mywiki.wooledge.org/WordSplitting
http://mywiki.wooledge.org/Quotes

Short form: double-quoting variables protects the contents from being word-split during expansion.

Problem solved. Thanks for the help! THe wiki site on double quotes were extremely helpful!