Finding Files and Binaries on Linux and UNIX

I manage a number of different types of systems. I have an Arch Linux laptop, a Macbook installed with OS X, CentOS and RHEL machines at work, as well as Debian servers both at work and home. As if that weren’t enough I also maintain a few FreeBSD servers. Between all of these different Operating Systems and variants I find that certain files and commands aren’t always where I might expect them to be. For today’s article I’ve outlined different methods for finding files and binaries on Linux and UNIX systems.

Locate

The first tool I’ll share is the locate command. This command searches through an index, built-daily, of all files and folders on your machine. Locate should be available on all standard UNIX systems, and is generally a very fast way to search for files.

• Positives: fast
• Negatives: not very specific, index updated daily

If you need to re-build your index to include recently added files, you can run the command:

updatedb

Find

The find command is much, much more granular than the locate command but it can also be more complicated to use. Explaining all of its options would warrant a post of its own, so I’ll just outline a few basic uses.

• Positives: very, very granular search parameters
• Negatives: slower than other methods

To use the find command, refer to one of these examples:

find / -type f -iname "httpd.conf"
find . -type f -name ".bashrc"
find /etc/ -type f -name "hosts.*"
find /usr/local/ -type d -iname "www"


These examples are all very similar, with only slight variations, to give you an idea of some of the power of find. Again, find can do much more than this, but this is enough to get you started.

• The first command searches from the root directory for any files (-type f) for the case-insensitive string of “httpd.conf”.
• The second command searches the current working directory for any files with the case-sensitive name of “.bashrc”.
• The third command searches within the /etc/ directory (and subdirectories) for any files matching the name “hosts.*”
• The last command searches within the /usr/local/ directory for any directories (-type d) with the case-insensitive name of “www”.

As you can see, find can be very flexible and this only touches on the advanced search patterns it can define. I highly suggest you have a look at the find man page for more information!

Which

The which command searches for binary files within your PATH. For example, let’s say you need to know the full path to the wget command. You could use:

which wget

You should see something along the lines of:

/usr/bin/wget

Binaries may be stored in different places on different systems, which is again why it is important to know how to find them. I use which frequently within my scripting in an attempt to make scripts portable. Let me give you an example:

#!/bin/bash
if [ -x $(which wget) ]; then
$(which wget) http://example.com/file.txt
fi

This very simply script doesn’t make any assumptions about the availability or the location of the wget tool. It does a simple check to see if the binary, as defined by its full path, is executable and if so use it to download a file. If wget does not exist the script will do nothing, and if it does exist it will be sure to execute it by its full path.

This tool has been helpful when moving between operating systems and variants. It helps me ensure I know exactly where files are, and not make any assumptions.

Whereis

The whereis tool is similar to the locate tool in that it is not as granular as find, and it is also similar to the which tool in that it searches only a predefined PATH for files. I use whereis constantly on my FreeBSD systems to search for ports within the ports tree. An example:

whereis portmaster

This would give me the output (assuming it is installed), of:

portmaster: /usr/local/sbin/portmaster /usr/local/man/man8/portmaster.8.gz /usr/ports/ports-mgmt/portmaster

This searches the standard binary, manual page, and source directories. As you can see from the above output, I have a result from each. This tells me where the binary is in its full path, where the man page(s) is stored as well as within the ports tree. If I didn’t have it installed, the only result I would be given would be the ports tree entry. This would help me find the path, allowing me to install it.

Conclusion

All of these tools are standard UNIX binaries that you should find on any system. Each tool has its own strengths and weaknesses, and none of them will always do the job the right way. I find myself using each of these on a regular basis, each for its own strengths. I would invite you to start using these commands in your day-to-day as needed, and read more about them.