[SOLVED] sed deletes extra lines

arun natarajan · 09-05-2016, 05:32 AM

hi,

when i am executing below sed command for deleting a single line which starts with "bin" and ends with "nologin". But it also deletes the next line from the matching pattern.

[root@node2 ~]# uname -a
Linux node2.cluster.com 2.6.32-71.el6.x86_64 #1 SMP Wed Sep 1 01:33:01 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux

[root@node2 ~]# rpm -qa sed
sed-4.2.1-5.el6.x86_64

before executing the cmd...

[root@node2 ~]# cat -n arun | head
1 root:x:0:0:root:/root:/bin/bash
2 root:x:0:0:root:/root:/bin/bash
3 root:x:0:0:root:/root:/bin/bash
4 root:x:0:0:root:/root:/bin/bash
5 root:x:0:0:root:/root:/bin/bash
6 root:x:0:0:root:/root:/bin/bash
7 bin:x:1:1:bin:/bin:/sbin/nologin
8 daemon:x:2:2:daemon:/sbin:/sbin/nologin
9 sync:x:5:0:sync:/sbin:/bin/sync
10 shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown

after executing a command

[root@node2 ~]# sed -i /^bin/,/nologin$/d arun

[root@node2 ~]# cat -n arun | head
1 root:x:0:0:root:/root:/bin/bash
2 root:x:0:0:root:/root:/bin/bash
3 root:x:0:0:root:/root:/bin/bash
4 root:x:0:0:root:/root:/bin/bash
5 root:x:0:0:root:/root:/bin/bash
6 root:x:0:0:root:/root:/bin/bash
7 sync:x:5:0:sync:/sbin:/bin/sync
8 shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
9 halt:x:7:0:halt:/sbin:/sbin/halt
10 mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
[root@node2 ~]#

it is suppose to delete only line number 7, but it also deletes line number 8, why ???

syg00 · 09-05-2016, 05:56 AM

Because you told it to. Read the documentation

Quote:

If the second address is a regexp, then checking for the ending match will start with the line following the line which matched the first address: a range will always span at least two lines (except of course if the input stream ends).

arun natarajan · 09-05-2016, 06:28 AM

ok got it.

but is there a way to delete a particular line alone, when lines are ending with same word.??

danielbmartin · 09-05-2016, 06:45 AM

Quote:

Originally Posted by arun natarajan

... deleting a single line which starts with "adm" and ends with "nologin".

Your sample input file contains no lines which start with adm.

Daniel B. Martin

danielbmartin · 09-05-2016, 06:47 AM

Quote:

Originally Posted by arun natarajan

but is there a way to delete a particular line alone, when lines are ending with same word.??

Consider grep.

Daniel B. Martin

syg00 · 09-05-2016, 07:09 AM

sed is the correct tool to update in-place. Selecting the line to delete simply requires correct specification of the line to delete - regex usually makes that easier. Don't specify a line range - just use the command to select the data to delete.

jostber · 09-19-2016, 07:05 AM

This should work better:

Code:

sed -i /^bin.*nologin$/d arun

pan64 · 09-19-2016, 07:38 AM

Quote:

Originally Posted by syg00

sed is the correct tool to update in-place. Selecting the line to delete simply requires correct specification of the line to delete - regex usually makes that easier. Don't specify a line range - just use the command to select the data to delete.

/etc/password is a file which must not be modified in-place. Just to be sure you did not make any mistake, otherwise you will not be able to login any more....
(yes, I know it was a copy of that file)

astrogeek · 11-06-2016, 01:42 PM

@jostber

Quote:

Originally Posted by arun natarajan

Thanks for your answer. Its working as expected.

@arun natarajan
Returning to say thank you is good form and always appreciated, but apparently you clicked Report instead of Quote or Reply.

If your original question is now resolved please use the Thread Tools option at top of this thread to mark it Solved.

Thanks!