CODEWITHSUNDEEP
regex
ravindrab
ravindrab

Reputation: 2772

Regular expression using '$' sign and '^'

Can some body explain the difference between below expressions please?

[0-9]{1,3}:[0-5][0-9]

^([0-9]{1,3}:[0-5][0-9])$

I don't get the exact usage of ^ sign and $ sign in regular expressions.

I observe that If I write the second expression as below, it didn't make any difference.

^([0-9]{1,3}):([0-5][0-9])$

Upvotes: 3

Views: 282

Answers (3)

Kent
Kent

Reputation: 195039

examples explain it clear: 

^     : matches the beginning of a line
$     : matches the end of a line

"^foo$" : matches "foo", but not " foo" or "xxfooyy"
"foo$"  : matches "foo",  " foo" or "xxfoo" but not "foobar"
"^foo"  : matches "foo",  "fooyy" or "foo " but not "xfoo"
"foo"   : matches "foo",  " foo" or "xxfooyy"

Upvotes: 4

Fabian Schmengler
Fabian Schmengler

Reputation: 24551

^ = start of string/line $ = end of string/line

So your first expression will also match "FOO123:12BAR"

The difference between your second and third expression is not in what they match but what they capture, as the parantheses for capture groups differ.

Upvotes: 2

Denys Séguret
Denys Séguret

Reputation: 382132

^ and $ are here the start and end of string anchors.

The second regular expression means you want to match the whole input.

Upvotes: 2

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