Locating files using the find command

The find command is a powerful utility that allows the user to find files located in the file system via criteria such as the file name, when file was last accessed, when the file status was last changed, the file’s permissions, owner, group, size.

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Find a file “foo.bar” that exists somewhere in the file system

find / -name foo.bar -print

On most platforms the -print is optional, however, on some systems nothing will be output without it. Without specifications find searches recursively through all directories.

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Find a file without searching network or mounted file systems

find / -name foo.bar -print -xdev

This is useful if you have network drives that you know the file would not be located on. “-mount” does the same thing as “-xdev” for compatibility with other versions of find.

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Find a file without showing “Permission Denied” messages

find / -name foo.bar -print 2>/dev/null

When find tries to search a directory or file that you do not have permission to read the message “Permission Denied” will be output to the screen. The 2>/dev/null option sends these messages to /dev/null so that the found files are easily viewed.

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Find a file, who’s name ends with .bar, within the current directory and only search 2 directories deep

find . -name *.bar -maxdepth 2 -print

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Search directories “./dir1” and “./dir2” for a file "foo.bar

find ./dir1 ./dir2 -name foo.bar -print

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Search for files that are owned by the user “skippie”

find /some/directory -user skippie -print

The files output will belong to the user “skippie”. Similar criteria are -uid to search for a user by their numerical id, -group to search by a group name, and -gid to search by a group id number.

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Find a file that is a certain type. “-type l” searches for symbolic links

find /any/directory -type l -print

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Several types of files can be searched for: Several types of files can be searched for:

• b block (buffered) special

• c character (unbuffered) special

• d directory

• p named pipe (FIFO)

• f regular file

• l symbolic link

• s socket

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Search for directories that contain the phrase “foo” but do not end in “.bar”

find . -name '*foo*' ! -name '*.bar' -type d -print

The “!” allows you to exclude results that contain the phrases following it.

find becomes extremely useful when combined with other commands. One such combination would be using find and grep together.

find ~/documents -type f -name '*.txt' \ -exec grep -s DOGS {} \; -print

SCP or (secure copy) allows you to move files even entire directories to, or from local and or remote hosts, using the same authentication and securtiy levels as SSH.

Copy the file “foobar.txt” from a remote host to the local host

    $ scp username@site.com:foobar.txt /local/directory

Copy the file “foobar.txt” from the local host to a remote host

    $ scp foobar.txt username@remotehost.com:/path/to/directory

Copy the directory “foo” from the local host to a remote host’s directory “bar”

    $ scp -r foo username@remotehost.com:/remote/directory/bar

Copy the file “foobar.txt” from remote host “site1.com” to remote host “site2.com”

    $ scp username@site1.com:/remote/directory/foobar.txt \username@site2.com:/remote/directory/

Copying the files “foo.txt” and “bar.txt” from the local host to your home directory on the remote host

    $ scp foo.txt bar.txt username@site.com:~

Copy the file “foobar.txt” from the local host to a remote host using port 1000 (or whatever ssh port your running on)

    $ scp -P 1000 foobar.txt username@site.com:/remote/directory

Copy multiple files from the remote host to your current directory on the local host

    $ scp username@site.com:/remote/directory/\{a,b,c\} .

    $ scp username@site.com:~/\{foo.txt,bar.txt\} .

By default scp uses the Triple-DES cipher to encrypt the data being sent. Using the Blowfish cipher has been shown to increase speed on slower connections. This can be done by using option -c blowfish in the command line.

$ scp -c blowfish file.txt username@site.com:~

Use the -C option for compression, and a bit of speed. If you have a fast connection you might not notice much of a difference. However it is a bit more CPU intensive due to the algorithms used to generate the encryption.

Blowfish scp example:

    $ scp -c blowfish -C file.txt username@site.com:~

Listing directory contents

ls - To list the contents of a directory

Usage: ls [flags]

Example: ls (To list the current directory)

Example: ls /tmp (To list the contents of /tmp)

Example: ls -a (To list hidden files)

Example: ls -l (To list file/directory permissions and file sizes)

Example: ls -al /tmp(To list all files and permissions in /tmp)

Example: ls -il (To get the inode number, permissions, owner, file sizes, UID and timestamps of all files in current directory)

For more information, in a terminal, type man ls

Deleting files

To delete a file you must first have write permission to it. Once you have write permission, in a terminal run:
rm filename\

There is no “Recycle Bin” in Linux so once you delete a file, it’s gone for good.

Being safe, find the files first and actually look at what you will be deleting! find . -type f -name foo\*

When removing files, you may use an astrix “*” as a wildcard flag to remove certain files, for example if I wanted to remove all files that began with “foo” , I would run:

find . -type f -name foo\* -exec rm {} \;

If anyone tells you to run rm -rf / as root, DO NOT LISTEN TO THEM. Running this command will delete all the files/directories on your Linux system. And render the machine completely useless with zero chance of recovery!

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You should not be running as root to begin with! Learn to use a secondary user, and as well the “su” command or “Super User” as general usage dictates.

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Deleting directories
If you have ownership to the directory and the directory is empty, you can simply type

rmdir directoryname to remove the directory.

If the directory is not empty and you wish to simply delete it and all its contents, run:

rm -rf directoryname\[/code\] Please be careful with the -rf flag, as it will remove everything in the specified directory including sub directories. With root access and the rm -rf command you can wipe out your entire system if you make an error.

Editing files
The default editor installed with most all distros of linux is VIM , or

vi filename

Vim is an advanced command line editor, you should consider learning the commands.

You can however also use nano To edit a file with nano, simply run:

nano filename

This will open up the file and allow to you edit the file. At the bottom of the screen you will notice the various commands that you have access to with nano. If you wish to save the file and exit, simply hold down the control key and hit the x key on your keyboard.

You will be asked to confirm this edit, if you have permissions to do so, once you confirm by typeing y, the file will be edited and nano will exit.

Renaming files
mv - Command used to move or rename files
Usage: mv file location
Usage: mv filename::newfilename

Example: mv tmp/site-logo.png /tmp/lime-it.png

Read the manual: man mv

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Moving files
mv - Used to move or rename files
Usage: mv file location (to move)

Example:mv index.html /var/www/index.html

For more information, in a terminal and read the manual pages, type: man mv

Downloading a file using the terminal command wget

First cd to the tmp directory

cd /tmp

Example: wget http://news.lime-it.us/uploads/system/site-logo.png

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Copy files

cp - Used to copy files or directories from one location to another. We can use the above example for this.

Example: cp /tmp/site-logo.png /var/www/httpdocs

[as httpdocs is your root web directory]

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To move ALL files from one directory to another:

Example: cp /tmp/files/* /var/www/httpdocs

(the “*” tells the machine to copy everything in /tmp/files to /var/www/)

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Check your man pages for more information on the cp command**

man cp

Adding a user
While logged in as root, type in the shell:

replace username with the username you wish

adduser username

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Deleting a user:
While logged in as root, type replace username with the user name you wish to delete.

userdel username

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Change login password
To set the password for a specific user, replace username with the name of the user. By typing simply:

  passwd username

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To change the current password for the user you are logged in as:

passwd

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Change directories

cd - Used to Change Directories

Usage: cd /[directory]
Example:

cd /tmp

Example:

cd ../

(moves back one directory)

Move to your home directory:

cd

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Check the man pages for more info:

man cd