Weblog entry #22 for Utumno
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#22
Sed advice
Posted by Utumno on Mon 12 Feb 2007 at 02:58
I've got a line that looks like this
(crap)7-digit-number-1(crap)7-digit-number-2(crap)....7-digit-number-n(crap)
and I would like to parse out the 1st 7-digit number out of this with sed. My problem is that sed, being greedy, always matches the last number, i.e. if I write
I am going to get the last 7-digit number rather than the first. I dont know how many 7-digit numbers are there in my line.
Anyone could shed some light on this?
(crap)7-digit-number-1(crap)7-digit-number-2(crap)....7-digit-number-n(crap)
and I would like to parse out the 1st 7-digit number out of this with sed. My problem is that sed, being greedy, always matches the last number, i.e. if I write
echo line | sed -n "s/.*\([0-9]\{7\}\).*/\1/p"
I am going to get the last 7-digit number rather than the first. I dont know how many 7-digit numbers are there in my line.
Anyone could shed some light on this?
Comments on this Entry
Posted by Anonymous (61.246.xx.xx) on Mon 12 Feb 2007 at 04:25
Maybe http://www.grymoire.com/Unix/Sed.html#uh-4 helps.
The approach to me seems to be to realize * is greedy, so logically keep away from the front.
BTW, if you occasionally use sed, you really should bookmark that site. Excellent introductory coverage of sed.
PJ
The approach to me seems to be to realize * is greedy, so logically keep away from the front.
BTW, if you occasionally use sed, you really should bookmark that site. Excellent introductory coverage of sed.
PJ
[ Parent | Reply to this comment ]
Try splitting the command into two:
cat line | sed -e "s/\([0-9]\{7\}\).*/\1/" -e "s/.*\([0-9]\{7\}\)/\1/"
M.
[ Parent | Reply to this comment ]
I know you are using sed but this could be also easily done using grep
grep -o "[0-9]\{7\}"
pyrrhic@Valhalla:~$ cat sedtest
asdasdfasdfasdf1234567dsdgfdsgf2345671dsfgsdfgsdfg3456712sdfgsdfg dsfg
pyrrhic@Valhalla:~$ cat sedtest |grep -o "[0-9]\{7\}"
1234567
2345671
3456712
adding a |head -1 would give you the first result.
grep -o "[0-9]\{7\}"
pyrrhic@Valhalla:~$ cat sedtest
asdasdfasdfasdf1234567dsdgfdsgf2345671dsfgsdfgsdfg3456712sdfgsdfg dsfg
pyrrhic@Valhalla:~$ cat sedtest |grep -o "[0-9]\{7\}"
1234567
2345671
3456712
adding a |head -1 would give you the first result.
[ Parent | Reply to this comment ]
Posted by Utumno (61.229.xx.xx) on Sat 17 Feb 2007 at 19:17
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Excellent advice, thanks.
[ Parent | Reply to this comment ]