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I'm trying to write a script that takes as input a set of integers representing certain /dev/sda's. For example, if the command line arguments are 3 & 5, the output will show the UUID for /dev/sda3 and /dev/sda5. My code is:

#!/bin/bash

### Shows UUID of input /dev's - REQUIRES SUDO

## Options:
## [-m] Multiple Devs   - returns both dev name and UUID
## [  ] No option       - returns only the UUID of the dev.

while getopts m: option
do
    case "${option}"
    in
    m)  echo -e "\nDEV\tUUID\n====\t================"
        blkid | grep .*sda[\"$@\"] | sed -r 's/\/dev\/([[:alnum:]]+).* UUID="([[:alnum:]]+)".*/\1\t\2/g'
        ;;
    esac
done

My primary problem is with the line grep .*sda[\"$@\"] which returns the following error:

$ sudo ./dUShow.sh -m 3 5

DEV     UUID
====    ================
grep: Unmatched [ or [^

Now if I'm not mistaken, this means the problem occurs when I'm trying to provide as alternative options *.sda[$@] which I want RegEx to overwrite with *.sda[$1$2], equivalent to *.sda[35] for the given input.

How do I do this?

Sample Input

sudo ./dUShow.sh -m 3 5

Desired output

DEV     UUID
====    ================
sda3    BC4208CF42089076
sda5    968E185A8E183569

Addendum

Is the expression .*sda[\"$@\"] going to produce *.sda[35] or *.sda[3 5]? If it is the latter, will it cause a problem? If so, how do I solve it?

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5
  • I would add -E to your grep command for a start Commented Sep 29, 2017 at 12:32
  • @RamanSailopal Really doesn't help at all! Why does this grep need Extended RegEx anyway? Commented Sep 29, 2017 at 12:37
  • First, sed doesn't need grep and second, to get the device name and UUID you definitely don't need blkid (nor root access for that matter): man lsblk is your friend... and btw, OR-ing patterns is done via | Commented Sep 29, 2017 at 12:43
  • @don_crissti thanks for the suggestions, but any way I could make this present script work? Commented Sep 29, 2017 at 12:52
  • Instead of doing the wrong thing the wrong way you should build up the command line arguments (e.g args like /dev/sd[a-z][0-9]+ and so on...) and then replace that entire nonsense with lsblk -o name,uuid "$@". A typical case of XY question... Commented Sep 29, 2017 at 13:45

2 Answers 2

Reset to default
2

If $1==3 and $2==5 then

grep .*sda[\"$@\"]

turns into

grep .*sda[3 5]

Which is a problem due to the lack of quotes. Try this instead:

regex=".*sda($( IFS='|'; echo "$*" ))\\>"     # => .*sda(3|5)\>
blkid | grep -E "$regex" | ...

The \> is a word boundary, to make the regex more precise.

Some documentation about GNU grep regular expression flavours:

  1. basic regular expressions
  2. extended regular expressions
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2
  • Thanks, that works perfectly! Could you please explain the line ".*sda($( IFS='|'; echo "$*" ))"? Commented Sep 29, 2017 at 13:03
  • If you echo "$regex" you can see the result. "$*" joins the positional parameters using the first char of IFS as the separator. I do that in a subshell to avoid changing IFS in the current shell Commented Sep 29, 2017 at 17:05
1

For single digit matches you can put the argument string straight into the RE brackets. (I think this is what you were originally trying to do.)

grep "/dev/sda[$*]:"

Note that $* will include a space character between digit arguments (for example, 2 and 5 will result in $* having the quoted value 2 5), but as we can guarantee that /dev/sda : will never match it doesn't matter in this situation.

To simplify the command line you can then dispense entirely with the grep, like this:

blkid | sed -rn "s#/dev/(sda[$*]):"'.* UUID="([[:alnum:]]+)".*#\1\t\2#p'
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