在awk命令中不能使用“（”

Question

I tried following awk command in my Linux box, it throws error.

awk -F "VALUES(" '{print $2}'

Error :

awk: fatal: Unmatched ( or \(: /VALUES(/

I also tried with back slash, its also not working.

awk -F "VALUES\\(" '{print $2}'

Error :

awk: warning: escape sequence `\(' treated as plain `(' 
awk: fatal: Unmatched ( or \(: /VALUES(/

Please let me know how to include ( in awk search string.

Answer 1

if the value of -F is longer than 1, it was considered as regex, so you need do something like:

regex character class:

kent$  echo "a foo( b"|awk -F"foo[(]" '{print $1,$2}'
a   b

escape the (

if you really want to escape the ( , you need:

kent$  echo "a foo( b"|awk -F"foo\\\\(" '{print $1,$2}'
a   b

or

kent$  echo "a foo( b"|awk -F'foo\\(' '{print $1,$2}'  
a   b

Answer 2

You're using Linux, so you're likely using gawk . From the gawk man page on my system:

   -F fs
   --field-separator fs
          Use fs for the input field separator (the value of the FS prede-
          fined variable).

and:

Fields

As each input record is read, gawk splits the record into fields, using the value of the FS variable as the field separator. If FS is a single character, fields are separated by that character. If FS is the null string, then each individual character becomes a separate field. Otherwise, FS is expected to be a full regular expression.

Since you've got multiple characters in your -F , it's being interpreted as a regular expression. And you have an opening bracket without a closing bracket.

You may be able solve this either by escaping the bracket ( "VALUES\\(" ), or by putting the bracket in a group ( "VALUES[(]" ). I recommend the latter, because escaping things with backslashes can be ugly and unpredictable, and will help point out to you that this is a regex, not a string, when you re-read this script a few months from now.