Bash match string with regex

Question

I am using bash 4.1.10(4)-release and I trying to use a regex to match against two capital letters [A-Z]{2} and then anything. So for example BXCustomerAddress, CAmaterial would be acceptable, but WarehouseMessage would not. I have the following script for testing purposes:

#!/bin/bash

if [[ "Ce" =~ [A-Z]{2} ]]; then
    echo "match"
fi

My questions are:

When I run this script, why does it return that I have a match?
Does anyone know how I could achieve my desired results?

Check .bash_profile or .bashrc if nocasematch or nocaseglob is enabled there. — konsolebox
– konsolebox, Commented Aug 15, 2014 at 17:28

anubhava · Accepted Answer · 2014-08-15 17:24:59Z

5

Looks like you have shopt nocaseglob turned on. Turn it off using:

shopt -u nocaseglob

Now [[ "Ce" =~ [A-Z]{2} ]] should not match and will return false.

answered Aug 15, 2014 at 17:24

anubhava

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9 Comments

konsolebox Over a year ago

Already about to answer :) I assumed nocaseglob is only for glob patterns.

anubhava Over a year ago

It seems both nocaseglob and nocasematch affect this behavior.

carl_corder Over a year ago

I just checked both options: $ shopt nocasematch $ shopt nocaseglob both were turned off. Then I tried to change the script by inlining both options: #!/bin/bash shopt -u nocaseglob shopt -u nocasematch if [[ "Ce"=~[A-Z]{2} ]]; then echo "match" fi But I get the same results.

chepner Over a year ago

@carl_corder Did you include whitespace around the =~ operator? Your comment indicates you didn't, although it was included in the original question. Without the whitespace, the expression is treated as a single non-empty string that always evaluates to true.

carl_corder Over a year ago

Interesting I used regedit to change the value of HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\kernel to 0, rebooted the machine. confirmed that the value is indeed zero. Ran the script again, same problem. I will keep you guys updated if I figure it out.

|

Michael Kohl · Accepted Answer · 2014-08-15 17:26:48Z

2

Check the value of the shell option nocasematch:

$ shopt nocasematch
nocasematch     off

answered Aug 15, 2014 at 17:26

Michael Kohl

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Comments

Robby Cornelissen · Accepted Answer · 2014-08-15 17:27:48Z

1

shopt nocasematch is probably set to on. Turn it off with

shopt -u nocasematch

From the Bash Reference Manual:

nocasematch

If set, Bash matches patterns in a case-insensitive fashion when performing matching while executing case or [[ conditional commands.

answered Aug 15, 2014 at 17:27

Robby Cornelissen

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1 Comment

carl_corder Over a year ago

I added both options to the .bashrc and it is still matching. I failed to mention that I am running the shell through cygwin (if it matters).

carl_corder · Accepted Answer · 2014-08-15 21:59:46Z

0

After trying out many different combinations, this is what gave me the expected behavior:

#!/bin/bash
# [A-Z][A-Z] will not work
# [:upper:][:upper:] will not work
# [[A-Z]][[A-Z]] will not work
# [[:upper:]][[:upper:]] does work

echo "test one"
if [[ "CA" =~ ^([[:upper:]][[:upper:]])+ ]]; then
    echo "match"
fi

echo "test two"
if [[ "Ce" =~ ^([[:upper:]][[:upper:]])+ ]]; then
    echo "match"
fi

I get the expected results of:

test one
match
test two

Thanks for everyone's help

answered Aug 15, 2014 at 21:59

carl_corder

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