2

The following is what I found after googling:

dpkg --list 'linux-image-*' \
    | perl -ane 'BEGIN { $r = `uname -r` or die; chomp $r } print $F[1], "\n" if $F[0] eq "ii" && $F[1] !~ /\Q$r\E\b/' \
    | xargs -r aptitude purge -y

Could someone combine the above 3 lines into one? I find it easier to copy and paste a single line into a sudo command than three lines, one at a time.

For Hauke Laging: I have edited this original post to include the error message when I tried to copy the three split lines at once following the sudo command:

username@hostname:~$ sudo -i
[sudo] password for username: 
root@hostname:~# dpkg --list 'linux-image-*' \
> 
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-=================================
un  linux-image-2. <none>                    (no description available)
un  linux-image-2. <none>                    (no description available)
un  linux-image-2. <none>                    (no description available)
un  linux-image-2. <none>                    (no description available)
ii  linux-image-3. 3.14.4-1~bpo amd64        Linux 3.14 for 64-bit PCs
ii  linux-image-3. 3.2.57-3+deb amd64        Linux 3.2 for 64-bit PCs
ii  linux-image-am 3.14+57~bpo7 amd64        Linux for 64-bit PCs (meta-packag
root@hostname:~#     | perl -ane 'BEGIN { $r = `uname -r` or die; chomp $r } print $F[1], "\n" if $F[0] eq "ii" && $F[1] !~ /\Q$r\E\b/' \
-bash: syntax error near unexpected token `|'
root@hostname:~# 
root@hostname:~#     | xargs -r aptitude purge -y
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2
  • 6
    Only the xargs above needs to run under sudo. Commented May 29, 2014 at 15:16
  • 2
    sudo aptitude purge -y "~i ^linux-image ! -$(uname -r)\$" Commented May 29, 2014 at 18:47

3 Answers 3

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6

There is no need to make one line out of those three. The shell removes the newline if it is escaped by \. In other words: A command with arguments over three lines of that kind "sees" only one line, not three.

The next problem is:

sudo cmd1 | cmd2 | cmd3

causes only cmd1 to run as root. You could do something like

sudo bash -c 'cmd1 | cmd2 | cmd3'

but that may cause quoting annoyances.

The probably easiest solution is: Create an empty file, copy the three lines into it and then run it with:

sudo bash file

use | for safe line breaks

You can put the | at the end of a line. That way there can be no problems with (additional) newlines. Try this:

dpkg --list 'linux-image-*' |
  perl -ane 'BEGIN { $r = `uname -r` or die; chomp $r } print $F[1], "\n" if $F[0] eq "ii" && $F[1] !~ /\Q$r\E\b/' |
  sudo xargs -r aptitude purge -y
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6
  • 2
    Also sudo sh << \E, paste and enter E. Commented May 29, 2014 at 15:40
  • @Huake Laging I know that a command with arguments over three lines of that kind "sees" only one line. The problem I have is to have to copy three lines, one at a time, into the sudo command. Commented May 29, 2014 at 16:58
  • @Patrick If you have the time, please help me out on this one. Thanks in advance. Commented May 29, 2014 at 16:58
  • @user66229 I don't know what you're talking about: I can easily copy three lines at once. Commented May 29, 2014 at 18:16
  • 2
    @user66229 That looks strange to me. The second line in the shell is > instead of > | perl -ane .... Thus it seems that there are two newlines between the commands, not just one. If you paste that into a file: Are there empty lines between the commands then? But this problem can be avoided by moving the |. I will add that to my answer. Commented May 30, 2014 at 12:40
5

Backslash-newline is a way to split lines in a place where the syntax would not normally allow a line break, so you could just remove that.

dpkg --list 'linux-image-*' | perl -ane 'BEGIN { $r = `uname -r` or die; chomp $r } print $F[1], "\n" if $F[0] eq "ii" && $F[1] !~ /\Q$r\E\b/' | xargs -r aptitude purge -y

If you want to run this under sudo, you can't just copy-paste that line after sudo, because only the dpkg command would then run as root. In fact, only aptitude needs to run as root.

dpkg --list 'linux-image-*' | perl -ane 'BEGIN { $r = `uname -r` or die; chomp $r } print $F[1], "\n" if $F[0] eq "ii" && $F[1] !~ /\Q$r\E\b/' | xargs -r sudo aptitude purge -y

This command is overly complex for what it does. The perl script filters some installed packages, but aptitude is perfectly capable of doing that filtering.

sudo aptitude purge -y "~i ^linux-image !?exact-name(linux-image-$(uname -r))"
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  • Thanks for your response. I don't know bash scripting at all and am new to Linux commands. Using your expertise, could you modify the 3 split lines, combine them into a single one and make it usable under the sudo command, ensuring that the single line gives the exact same result as the original 3 split lines? Thanks in advance. Commented May 30, 2014 at 4:05
1

You can create a function too (see below).

You can put it in a file, e.g. ~/MyPersonalFunctions, in which you will add with time all the functions you will need to use.

You can load it only when you need with the command source ~/MyPersonalFunctions and you will have your extended set of functions.
You can even load it each time automatically writing source ~/MyPersonalFunctions in the file ~/.bashrc.

Note: You have to write the full path where you put this file. E.g if you put it in your ~/bin directory you will write source ~/bin/MyPersonalFunctions). 

function PurgeKernels()
{
dpkg --list 'linux-image-*' \
    | perl -ane 'BEGIN { $r = `uname -r` or die; chomp $r } print $F[1], "\n" if $F[0] eq "ii" && $F[1] !~ /\Q$r\E\b/' \
    | xargs -r sudo aptitude purge -y
}

function Cat(){  # Just to show you can put in the same file 
  echo Meow      # more than one function... :-)
}

Of course you can use it with the shorter version of the code proposed by the other answer in this page.

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