linking of grep command

[ishu2021]

how the grep command search when particular word is bing asked to search.what is the linking procedure to reach the particular word?

[waterhead]

I am not the most knowledgeable person on this, but I can tell you how I have learned to use it.

I usually use it in conjunction with another command, to pick out a certain word that I am looking for. This is done by separating the commands with a vertical line or "pipe". A space must be on either side of the pipe.

I often use it to see which firmware is loading on a system. The output of the dmesg command would give this, but it is a lengthy output. by using grep, I can get only the info that I want.

dmesg | grep firmware

When searching a text file for a word, use the cat command. I have blacklisted a wireless driver module, so to view if it actually is, I could do this:

cat /etc/modprobe.d/blacklist.conf | grep ath

The output of that is this:

cat /etc/modprobe.d/blacklist.conf | grep ath
blacklist ath_pci

I hope this helps you some.

[D-cat]

Grep is a filter. It's purpose is to limit the output to only lines containing your search word. By linking, I think you are reffering to what we call a pipe (|) which "links" or "pipes" the output from one command into the input of another. This can be useful when searching for a particular file or better, exact command.

Say I want to know exactly what commands are available to me with the string "ed" in them. I could do a simple find with grep:

find / | grep ed

but then the output could be enormous and include all files with "ed", I just want commands, so then I pipe that output into grep again:

find / grep ed | grep bin

Now the ouput will only be commands (or at least files in a "bin" directory) that include "ed" as part of their name.

Now, in my case, I still ended up with a lot of stuff I didn't need, so there's another feature to grep, where you can invert it (don't show lines contining...)

find / | grep ed | grep bin\/ | grep -v bino | grep -v lib\/
example:

dcat@Server:~> find / | grep ed | grep bin\/ | grep -v bino | grep -v lib\/
/bin/ed
/bin/sed
/bin/setleds
/opt/kde3/bin/digikamthemedesigner
/opt/kde3/bin/feedbrowser
/opt/kde3/bin/kcontroledit
/opt/kde3/bin/kded
/opt/kde3/bin/kdedoc
/opt/kde3/bin/keditbookmarks
/opt/kde3/bin/keditfiletype
/opt/kde3/bin/keduca
/opt/kde3/bin/keducabuilder
/opt/kde3/bin/kfiledialog
/opt/kde3/bin/kio_media_mounthelper
/opt/kde3/bin/kio_media_realfolder
/opt/kde3/bin/kmenuedit
/opt/kde3/bin/kryptomedia
/opt/kde3/bin/kspaceduel
/opt/kde3/bin/noteedit
/opt/picasa/bin/mediadetector
/opt/picasa/wine/bin/regedit
/opt/picasa/wine/bin/winedbg
/opt/picasa/wine/bin/winedumpfontver
/sbin/lvreduce
/sbin/vgreduce
/usr/bin/3Ddiag.ignoredb
/usr/bin/beagled
/usr/bin/btedit
/usr/bin/ccmakedep
/usr/bin/checkmedia
/usr/bin/combinedeltarpm
/usr/bin/devede
/usr/bin/dh_undocumented
/usr/bin/dvd+rw-mediainfo
/usr/bin/ed
/usr/bin/edit
/usr/bin/edit-xml-catalog
/usr/bin/editcap
/usr/bin/editres
/usr/bin/embedspu
/usr/bin/exrmaketiled
/usr/bin/fileschanged
/usr/bin/freedup
/usr/bin/frozen-bubble-editor
/usr/bin/gccmakedep
/usr/bin/gedi
/usr/bin/gnome-desktop-item-edit
/usr/bin/gnome-gen-mimedb
/usr/bin/gst-feedback
/usr/bin/gst-feedback-0.10
/usr/bin/gsvnsimplediff
/usr/bin/gtkhtml-editor-test
/usr/bin/gweled
/usr/bin/hal-is-caller-locked-out
/usr/bin/hal-is-caller-privileged
/usr/bin/hp-timedate
/usr/bin/icedax
/usr/bin/ipod-read-sysinfo-extended
/usr/bin/kded4
/usr/bin/kmenuedit
/usr/bin/ldbedit
/usr/bin/lilypond-invoke-editor
/usr/bin/localedef
/usr/bin/makedeltaiso
/usr/bin/makedeltarpm
/usr/bin/makedepend
/usr/bin/makedvd
/usr/bin/mcedit
/usr/bin/mediasort.sh
/usr/bin/movie-fakewavspeed
/usr/bin/nm-connection-editor
/usr/bin/nxredir
/usr/bin/pamedge
/usr/bin/pbmreduce
/usr/bin/pcprofiledump
/usr/bin/pdbedit
/usr/bin/pdfedit
/usr/bin/pfaedit
/usr/bin/pgmedge
/usr/bin/pm-is-supported
/usr/bin/pnmscalefixed
/usr/bin/psed
/usr/bin/pstoedit
/usr/bin/ptked
/usr/bin/red
/usr/bin/regedit
/usr/bin/scrollkeeper-get-extended-content-list
/usr/bin/sed
/usr/bin/shred
/usr/bin/sonic_reducer
/usr/bin/sudoedit
/usr/bin/tagmedia
/usr/bin/tiffmedian
/usr/bin/timed-read
/usr/bin/timed-run
/usr/bin/torcs-car-setup-editor
/usr/bin/tred
/usr/bin/updatedb
/usr/bin/upssched-cmd
/usr/bin/ustunts3dedit
/usr/bin/ustuntstrackedit
/usr/bin/winedbg
/usr/bin/winedump
/usr/bin/wired
/usr/bin/xdbedizzy
/usr/bin/xedit
/usr/bin/xkbvleds
/usr/bin/yuvmedianfilter
/usr/local/bin/Ted
/usr/sbin/aa-unconfined
/usr/sbin/grub-install.unsupported
/usr/sbin/gss_destroy_creds
/usr/sbin/parted
/usr/sbin/saned
/usr/sbin/susedig.sh
/usr/sbin/unconfined
/usr/sbin/upssched
/usr/share/dosemu/drive_z/bin/edit.cfg
/usr/share/dosemu/drive_z/bin/edit.exe
/usr/share/dosemu/drive_z/bin/edit.hlp
/usr/share/dosemu/drive_z/bin/edlin.exe
/usr/share/susehelp/cgi-bin/advancedsearch.cgi
dcat@Server:~>

This also shows another feature, the escape character.

Often, special characters are ignored or interpreted different. A "\" in front of certain characters like space, "/" , "." , etc. will make them process litterally.

There's other useful features to grep as well, as in usually the search is case sensitive, but if you add "-i" then it will ignore the case.

man grep for more info.