CODEWITHSUNDEEP
regexbashunixgrep
Murph_Fish
Murph_Fish

Reputation: 359

UNIX: How would I grep in a script using a variable as a search parameter for a file?

Before I Start, this isn't exactly how it seems and I did search the web for a while before coming here. Basically I have a script where the user passes in a string and stores it in a variable. I then have to take that word and search for all the subwords that could be made from it in a dictionary file. The problem I am having is I need to make sure the words are at least 4 characters long. I do not have the best grasp on regular expressions. I'm aware of the techniques you can use just logically can't piece it together sometimes. I will show you the line of code and explain my reasoning behind why I think it should be this way. Then, could someone correct me on my logic? I am not looking for someone to send me the working line of code but perhaps correct my logic so I can understand better and derive the answer on my own.

words=$(grep -iE '(["$text"]{4,})' /usr/dict/words)
echo "$words"

For example if I pass in string college I should get output like cell cello clee cleg etc.....

I am storing the command in another variable to echo. I am not sure why exactly, It just seems from what I saw online most people were rather fond of this. Using grep with -i for ignore case and -E for regular expression or (egrep) I believe the expression needs to be enclosed in single quote parenthesis for expressions. $text is the variable I stored the users input in. I know $ usually signifies the ending in and [] is a range and "" makes it read the variable rather than print what is there. Then {4,} meaning four or more characters. then the last part is the path to the file. Any input would be appreciated and again, I do not like being spoon fed answers it's an easy way to learn nothing. I would just like corrections on my logic if all possible. Thanks everyone!!

Upvotes: 1

Views: 1014

Answers (1)

unconditional
unconditional

Reputation: 7656

If by "subwords" you mean permutations of its letters, then your command is fine except for the quotes. Unfortunately you have to do it like this:

words=$(grep -iE '(['"$text"']{4,})' /usr/dict/words)

This way you pass to grep the single quoted string so that the shell doesn't interpret its special symbols. But at the same time you have to expand your $text var, thus you have to make a gap inside your single-quoted string, and in that gap place your variable in double quotes.

Hope I didn't spoil it for you.

Upvotes: 1

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