Bash Commands – How to Act on the Results of the Locate Command

bashcommand linegreplocateUbuntu

I'm trying to find where check_dns is defined in nagios' commands.cfg file, although there are quite a few files.

I know I could run something like find / -name "command.cfg" -exec grep check_dns {} \; to search for matches, but if possible I would like to use locate since it is an indexed copy and much faster.

When I run locate commands.cfg I get the following results:

/etc/nagios3/commands.cfg
/etc/nagiosgrapher/nagios3/commands.cfg
/usr/share/doc/nagios3-common/examples/commands.cfg
/usr/share/doc/nagios3-common/examples/template-object/commands.cfg
/usr/share/nagiosgrapher/debian/cfg/nagios3/commands.cfg
/var/lib/ucf/cache/:etc:nagiosgrapher:nagios3:commands.cfg

Is it possible to run locate and pipe it to an inline command like xargs or something so that I can grep each of the results? I realize this can be done with a for loop but I'm looking to pick up some bash-fu / shell-fu here more than how to do it for this specific case.

Best Answer

Yes, you can use xargs for this.

For example a simple:

$ locate commands.cfg | xargs grep check_dns

(When grep sees multiple files it searches in each one and enables filename printing along matches.)

Or you can explicitly enable filename printing via:

$ locate commands.cfg | xargs grep -H check_dns

(Just in case one grep is called only with 1 argument by xargs)

For programs that only accept one filename argument (unlike grep) you can restrict the number of supplied arguments like this:

$ locate commands.cfg | xargs -n1 grep check_dns

That does not print the names of files where matched lines are from.

The result is equivalent to:

$ locate commands.cfg | xargs grep -h check_dns

With a modern locate/xargs you can also protect against whitespace issues:

$ locate -0 commands.cfg | xargs -0 grep -H check_dns

(By default whitespace separates input of xargs - which is of course a problem when your filenames contain whitespace ...)

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No need to use a for-loop here, you can just use find:

sudo find /var/log/ -type f -regex '.*\.[0-9]+\.gz$' -delete

However, as it was suggested, check the manual page of logrotate for ways to reduce the number of files.

Bash – Quick way to open results from `find` or `locate`

I've had this in my ~/.screenrc for a while:

bind -c pasteline 1 eval copy 'stuff "-Y"' 'paste .'
bind -c pasteline 2 eval copy 'stuff "2-Y"' 'paste .'
bind -c pasteline 3 eval copy 'stuff "3-Y"' 'paste .'
bind -c pasteline 4 eval copy 'stuff "4-Y"' 'paste .'
bind -c pasteline 5 eval copy 'stuff "5-Y"' 'paste .'
bind -c pasteline 6 eval copy 'stuff "6-Y"' 'paste .'
bind -c pasteline 7 eval copy 'stuff "7-Y"' 'paste .'
bind -c pasteline 8 eval copy 'stuff "8-Y"' 'paste .'
bind -c pasteline 9 eval copy 'stuff "9-Y"' 'paste .'
bindkey ¬ command -c pasteline

Basically, typing ¬1 from within screen, inserts the first line above the cursor, ¬2 the second line and so on.

In my ~/.Xdefaults, I also have:

XTerm.VT100.translations:             #override\
    Meta <KeyPress> /: dabbrev-expand()

Which lets xterm complete (upon Alt+/) on what's on the screen (looking backward from the cursor position).

With zsh, when used within screen, you could do:

copy-screen() {
  screen -X eval copy 'stuff "-$ H\r"' 'writebuf .lastoutput'
  killring=(${(Oaf)"$(<~/.lastoutput)"})
  CUTBUFFER=$killring[1]
  killring[1]=()
}
zle -N copy-screen
bindkey '\ec' copy-screen

to bind Alt+C to that widget that stores the lines above the cursor into the cut buffer and the kill ring (what you paste with Ctrl+Y and cycle through with Alt+Y in emacs mode). (the above assumes screen was started from your home directory).

If the inserted text needs to be quoted (because it contains spaces or other special shell characters for instance), you can type Alt+" for zsh to quote it.

As an example, you've just run:

$ find /usr/local -size +1M
/usr/local/lib/liblzma.a
/usr/local/share/doc/sudo/ChangeLog
/usr/local/share/perl/5.18.2/Unicode/Unihan/Definition.db
/usr/local/share/perl/5.18.2/Unicode/Unihan/RSKangXi.db
/usr/local/share/perl/5.18.2/Unicode/Unihan/IRG_TSource.db
/usr/local/share/perl/5.18.2/Unicode/Unihan/HanYu.db
/usr/local/share/perl/5.18.2/Unicode/Unihan/RSUnicode.db
/usr/local/share/perl/5.18.2/Unicode/Unihan/IRG_GSource.db
/usr/local/share/perl/5.18.2/Unicode/Unihan/IRGKangXi.db
/usr/local/share/perl/5.18.2/Unicode/Unihan/IRGHanyuDaZidian.db

And you want to open vim on that sudo ChangeLog above. With the first approach you'd type:

vim ¬9

With the second approach:

vim /usAlt+/

And repeat that Alt+/ until you get to the changelog.

With the third approach:

vim Alt+CCtrl+YAlt+Y

And repeat that Alt+Y until you get to the changelog.

The last approach can be used for your $s1 query.

Instead of storing in the killring array, store in an array (like $s) and use $s[1] for the first line, $s[2] for the second...

copy-screen() {
  screen -X eval copy 'stuff "-$ H\r"' 'writebuf .lastoutput'
  s=(${(Oaf)"$(<~/.lastoutput)"})
}
zle -N copy-screen
bindkey '\ec' copy-screen

That Alt+C stores the lines above the cursor in the s array.

In any case, what we're retrieving is what is displayed on the screen, which is not necessarily the same as what the last command output. For instance printf 'a\bc \n' outputs 5 bytes a, BS, c, SPC and LF, but displays just a c.

Best Answer

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