Writing a bash script that accepts multiple multi-spaced arguments

Question

An example from (the excellent) Unix Programming Environment considers an address book:

 John Perkins 616-555-4444
 Bill Jotto 773-222-1112
 Dial-a-Clown 738-224-5823
 Prince Alex 837-999-999
 Pizza Hut 833-339-222
 Pizza Puk 882-922-222
 Pizza Buk 822-221-111

now I am writing a program that searches this address book called '411'

   grep $* /file/location/411

now running 411 will yield

 $> 411 John
 >John Perkins 616-555-4444

now say I want to call John and invite him for some pizza (So I am searching for John number and Pizza numbers).

 $>411 John Pizza
 grep: can't open pizza

No match!

So how to I tell the shell to accept multiple argument with arbitrary spaces?

When you wrote $>411 John Perkins Pizza did you mean $>411 John Pizza? Otherwise both Perkins and Pizza should have generated errors. — Adam Liss
– Adam Liss, Commented May 13, 2012 at 22:26

Adam Liss · Accepted Answer · 2012-05-14 18:35:29Z

3

When you call grep with more than one argument, it assumes the first is the pattern and all others are the files to be searched. You'll need to make two modifications:

When you call your program, you'll need to enclose multi-word arguments in double-quote characters. This is standard shell behavior.
Your program will need to read the arguments from the command line and either send them individually to grep or build a compound expression (arg1|arg2|arg3) and pass it to grep with the -E (extended regex) flag.

For example:

args="$1"
shift   # $2 becomes $1, $3 becomes $2, and so on
while [ -n "$1" ]; do
   args="$args|$1"
   shift
done

grep -E "$args" /path/to/address/book

Or:

while [ -n "$1" ]; do
  grep "$1" /path/to/address/book
  shift
done

edited May 14, 2012 at 18:35

answered May 13, 2012 at 22:25

Adam Liss

48.5k13 gold badges115 silver badges154 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

raam86 Over a year ago

What if I want an arbitrary number of arguments?

raam86 Over a year ago

Cool! The funny thing is the review loops right in the next section and I just didn't make the connection. Thanks a lot.

Asherah Over a year ago

"standard linux behavior". You probably mean "standard shell behaviour". Linux doesn't care what shell you use, or how or if that shell processes arguments.

tripleee Over a year ago

Shouldn't that be uppercase -E, or explicitly call egrep?

Collectives™ on Stack Overflow

Writing a bash script that accepts multiple multi-spaced arguments

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related