Four Ways to Find Commands and Find Files in Linux

Learn to Find Linux Commands and Files Faster

Beginner

Video Tutorial

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Four ways to find commands and find files in Linux | Linux Tutorial for Beginners (4:52)

Code Examples and Video Script

Welcome. Today's question: How do you find commands in Linux?

I'm Paul, and I think the greatest challenge for those transitioning from Mac and Windows, to Linux, is knowing what's available beyond that intimidating command prompt.

Step 1 - Overview of 4 Linux Commands for Search

So in this tutorial, I'll demonstrate four ways to filter through the 900, or so, commands so you can zero in on what you want to do.

We'll practice commands at the Terminal.

apropos
locate
find
which

Then review commands used earlier, and a cheat sheet.

cal
cd
ls
whatis
nano
clear
exit

And because the command line is difficult to master and we intend to go pretty far here, I will dedicate a few tutorials to finding help. Here we will focus on finding commands, and in the next tutorial we'll cover finding help on how to use those commands.

Step 2 - Practice With the apropos and locate Commands

Okay, so I've logged in to a local Linux server in my office, on this rainy day in California.

paul@fullstack:~$ cal February 2017 Su Mo Tu We Th Fr Sa 1 2 *3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Let's start with pwd to see where we sit in the directory structure, change directories to notes for later and ls to see what's in here.

paul@fullstack:~$ pwd /home/paul paul@fullstack:~$ cd notes paul@fullstack:~/notes$ ls video0002.txt video0004.txt video0006.txt video0008.txt video0011.txt video0003.txt video0005.txt video0007.txt video0009.txt video0012.txt paul@fullstack:~/notes$ clear

The Linux apropos command to search names and descriptions

Okay, Linux is obediently waiting for us now, so let's start with a beginner-level command, apropos, to see what's available once we have a topic in mind.

paul@fullstack:~/notes$ whatis apropos apropos (1) - search the manual page names and descriptions

Let's say we want to do something with 'search'. So the term search is an argument.

paul@fullstack:~/notes$ apropos search apropos (1) - search the manual page names and descriptions badblocks (8) - search a device for bad blocks bzegrep (1) - search possibly bzip2 compressed files for a regular expression bzfgrep (1) - search possibly bzip2 compressed files for a regular expression bzgrep (1) - search possibly bzip2 compressed files for a regular expression Class::ISA (3pm) - report the search path for a class's ISA tree exigrep (8) - Search Exim's main log exiqgrep (8) - Search in the exim queue find (1) - search for files in a directory hierarchy lzegrep (1) - search compressed files for a regular expression lzfgrep (1) - search compressed files for a regular expression lzgrep (1) - search compressed files for a regular expression manpath (1) - determine search path for manual pages oldfind (1) - search for files in a directory hierarchy xzegrep (1) - search compressed files for a regular expression xzfgrep (1) - search compressed files for a regular expression xzgrep (1) - search compressed files for a regular expression zegrep (1) - search possibly compressed files for a regular expression zfgrep (1) - search possibly compressed files for a regular expression zgrep (1) - search possibly compressed files for a regular expression paul@fullstack:~/notes$ clear

It returns roughly 20 commands that include the term 'search' in the description, or command name.

Let's try ssh, which is the secure protocol I'm using currently to communicate to this server.

paul@fullstack:~/notes$ apropos ssh authorized_keys (5) - OpenSSH SSH daemon rlogin (1) - OpenSSH SSH client (remote login program) rsh (1) - OpenSSH SSH client (remote login program) slogin (1) - OpenSSH SSH client (remote login program) ssh (1) - OpenSSH SSH client (remote login program) ssh-add (1) - adds private key identities to the authentication agent ssh-agent (1) - authentication agent ssh-argv0 (1) - replaces the old ssh command-name as hostname handling ssh-copy-id (1) - use locally available keys to authorise logins on a remote machine ssh-keygen (1) - authentication key generation, management and conversion ssh-keyscan (1) - gather ssh public keys ssh-keysign (8) - ssh helper program for host-based authentication ssh-pkcs11-helper (8) - ssh-agent helper program for PKCS#11 support ssh_config (5) - OpenSSH SSH client configuration files sshd (8) - OpenSSH SSH daemon sshd_config (5) - OpenSSH SSH daemon configuration file paul@fullstack:~/notes$ clear

And last let's try apropos find.

paul@fullstack:~/notes$ apropos ssh Devel::InnerPackage (3pm) - find all the inner packages of a package exinext (8) - Finding individual retry times exiwhat (8) - Finding out what Exim processes are doing find (1) - search for files in a directory hierarchy find2perl (1) - translate find command lines to Perl code findaffix (1) - Interactive spelling checking findfs (8) - find a filesystem by label or UUID findmnt (8) - find a filesystem locate (1) - find files by name mlocate (1) - find files by name oldfind (1) - search for files in a directory hierarchy pidof (8) - find the process ID of a running program. systemd-delta (1) - Find overridden configuration files xdg-user-dir (1) - Find an XDG user dir paul@fullstack:~/notes$ clear

Good, now, let's focus on the command near the middle, called locate.

The Linux locate command to find files

The locate command is a more of an intermediate-level command that searches a database of path names and returns a hit any time the argument shows up. So it can find more than just commands, but files and directories too. We can use locate to find commands using a trick, because in Linux, commands are normally located in a directory called bin.

paul@fullstack:~/notes$ whatis locate locate (1) - find files by name

Step 3 - Learn Faster with Reference Materials

Let me clarify with a Cheat Sheet I mentioned. I put this together for this purpose, as it has short definitions for 100 commands, plus links to videos and web pages in our Linux Essentials Playlist on YouTube. And here are commands in the Help section.

Linux Help Commands

apropos - search manual titles and descriptions
find - search for files within directories
man - view the online reference manuals
type - show a command's type and location
whatis - display one-line manual page descriptions
whereis - locate binaries, manuals and source code
which - locate commands

You will also find links to quizzes, wildcards, and what I wanted you to see is a common directory structure for most Linux distributions. Wherever you see bin, is where program binaries are stored. So here is /bin, another called /sbin and another pair of /usr/bin and /usr/sbin directories in the /usr directory.

So going back, if we use locate bin/nano.

paul@fullstack:~$ locate bin/nano /bin/nano /usr/bin/nano paul@fullstack:~/notes$ clear

Look, it shows up in two locations.

Two more points about locate. First, for it to work a database must be created. For example, when I tried locate on the same day as my installation, it failed.

Second, security. Some administrators remove locate on public-facing servers.

Step 4 - See the find Command in Action and Introduce which

The Linux find command to search for any type of file

Let's move on to the advanced command called find, that allows you to search for programs, or any type of file in a directory hierarchy. And rather than searching a saved database, it proceeds through the directories below where you point. The find command also gives you the capability to use regular expressions, like wildcards mentioned earlier, allowing for custom searches.

paul@fullstack:~/notes$ whatis find find (1) - search for files in a directory hierarchy paul@fullstack:~/notes$ ls video0002.txt video0004.txt video0006.txt video0008.txt video0011.txt video0003.txt video0005.txt video0007.txt video0009.txt video0012.txt paul@fullstack:~/notes$ find /home -name 'video001*' /home/paul/notes/video0012.txt /home/paul/notes/video0011.txt

Let's try two, searching through recent /notes. Here's the syntax, it goes find, location /home, category is -name, and the expression is video001* using the * wildcard.

Second, we could do this, to find files larger than 500 bytes.

paul@fullstack:~/notes$ find -size +500c . ./video0004.txt paul@fullstack:~/notes$ clear

The which command to find which program Linux will run

Okay next is which. Let's do an apropos editor, as in text editor, and there are 15 on my distribution, and nano is the one I suggest for beginners.

paul@fullstack:~/notes$ apropos editor editor (1) - Nano's ANOther editor, an enhanced free Pico clone ex (1) - Vi IMproved, a programmers text editor nano (1) - Nano's ANOther editor, an enhanced free Pico clone pico (1) - Nano's ANOther editor, an enhanced free Pico clone psed (1) - a stream editor rnano (1) - Restricted mode for Nano's ANOther editor, an enhanced free Pico clone rview (1) - Vi IMproved, a programmers text editor rvim (1) - Vi IMproved, a programmers text editor s2p (1) - a stream editor sed (1) - stream editor for filtering and transforming text select-editor (1) - select your default sensible-editor from all installed editors sensible-editor (1) - sensible editing, paging, and web browsing vi (1) - Vi IMproved, a programmers text editor view (1) - Vi IMproved, a programmers text editor vim (1) - Vi IMproved, a programmers text editor paul@fullstack:~/notes$ whatis which which (1) - locate a command paul@fullstack:~/notes$ which nano /usr/bin/nano paul@fullstack:~/notes$ locate nano /bin/nano /usr/bin/nano

The reason I bring it up is because which tells you which program Linux runs. Wait, remember earlier we saw two nano programs? I'm out of time here, but will answer this question in the next tutorial.

Step 5 - Next up: Finding options and arguments for commands

So here's a picture of our stack and where we're headed, one step at a time.

Client : HTML, CSS, JavaScript
Software : Python Scientific Stack
Data : PostgreSQL, MySQL
OS : Linux (command line), Debian

Next, we'll explore how to find help on using commands.

Have a nice day.

Four Ways to Find Commands and Files in Linux