正则表达式使用sed和/或grep

Question

How can I display the arch and version of queried rpm package using sed or grep?

[root@kitchen-vm-centos6-box boot]# rpm -qa | grep kernel-devel
kernel-devel-2.6.32-642.11.1.el6.x86_64
kernel-devel-2.6.32-696.10.2.el6.x86_64

What i need only is:

2.6.32-642.11.1.el6.x86_64

What is missing in my sed? => sed 's/[^\\.]\\+\\.//'

Thanks in advance!

Answer 1

你也可以使用cut：

rpm -qa | grep kernel-devel | cut -d \- -f 3-4

Answer 2

You can use sed as this and avoid en extra grep :

rpm -qa | sed '/kernel-devel/s/^[^0-9]*//'

2.6.32-642.11.1.el6.x86_64
2.6.32-696.10.2.el6.x86_64

Answer 3

Your sed removes the first dot after the first "2", because it's matched by the regex you provided.

You can fix easily by making the regex more explicit.

Other answers already suggested solutions, here's another one using grep :

$ rpm -qa | grep -oP "devel-\K(.*)"
2.6.32-642.11.1.el6.x86_64
2.6.32-696.10.2.el6.x86_64

\\K tells the engine to pretend that the match attempt started at this position (that's the alternative that Perl suggested for lookbehind).

Answer 4

You can do it with grep only:

rpm -qa |  grep -P -o '(?<=kernel-devel-).*'

Explanation:

• -o is match only. Ie grep will return the matched part only
• -P is perl regex mode. It enables lookarounds.
• (?<=...) is lookbehind. Ie stuff before the match. This is not part of the match so -o is not going to retain it

Of course, sed can help too:

rpm -qa | grep 'kernel-devel' | sed 's/^[^.0-9]*-//g'

Explanation:

• ^ matches the start of the string
• [^.0-9] matches the non-dot, non-number characters from the start of the string. This is the part that we don't need.
• The //g ending of the sed command replaces the matched part with empty string

Answer 5

One in awk:

$ rpm -qa | awk 'match($0,/^kernel-devel-./){print substr($0,RLENGTH)}'
2.6.32-642.11.1.el6.x86_64
2.6.32-696.10.2.el6.x86_64

Explained:

match($0,/^kernel-devel-./) {    # if the record starts with kernel-devel-[ANYTHING]
    print substr($0,RLENGTH)     # print starting from the [ANYTHING]
}