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====== Find Stuff in Linux ======

There are four basic commands to find stuff in Linux: 
  - whereis
  - which
  - locate 
  - find

===== whereis =====

Searches for binary files, source files, and man pages for the specified command names. Switches:
  * ''-b'' searches for binaries
  * ''-s'' searches for source files
  * ''-m'' searches for manuals

**Examples:**

<code>
whereis ls     # lists binaries, source and manuals if they exist
whereis -b ls  # lists only the binaries
whereis -s ls  # lists only the source files
whereis -m ls  # lists only the man files, if they exist
</code>

----

===== which =====

Returns the path to the executable indicated. 

**Example:** If you want to know which version of Python is called when you type in "python" at the command line...

<code>which python</code>

----

===== locate =====

Fast way to search for files by name on your disk. 

**Important:** Update the database before first ''locate'' and after significant changes on your disk.

<code>updatedb  # as root</code>

''locate'' will match the pattern you give it. So you may need to pipe to ''grep'' or provide a more specific search patter. Example: 

<code>locate python  # locates all file names that include 'python'</code>

----

===== find =====

==== Basic Syntax ====

<code>
find /path/to/search/ -name searchTerm
# 1. The first part is the 'find' command itself
# 2. The second part is where to start searching from
# 3. The third part is an expression that determins what to find
# 4. The fourth part is the name of the file to find
</code>

If you get a bunch of garbage on the screen, send stderr (by its file descriptor number: 2) to /dev/null:

<code>find /path/to/search/ -name searchTerm 2>/dev/null</code>

https://www.cyberithub.com/find-command-in-linux/

The -exec flag to find causes find to execute the given command once per file matched, and it will place the name of the file wherever you put the {} placeholder. The command must end with a semicolon, which has to be escaped from the shell, either as \; or as ";".

Syntax to be used for find exec multiple commands:

<code>find {PATH} [OPTIONS] -exec {COMMAND} {} ;</code>

**The first argument** after the find command is the location you wish to search. Although you may specify a specific directory, you can use a metacharacter to serve as a substitute. The three metacharacters that work with this command include:
  * Period (.): Specifies the current and all nested folders.
  * Forward Slash (/): Specifies the entire filesystem.
  * Tilde (~): Specifies the active user's home directory.

Find all files (not directories or links) of 1033 bytes in size that are not executable and which can be read (i.e., you can cat the file and read the contents):

<code>find . -type f -size 1033c ! -executable -exec cat {} \;</code>

----

==== Search Location Shortcuts ====

The first argument after the find command is the location you wish to search (the starting point, and find will recurse into subdirs). 
  * You may specify a specific directory path, or
  * You can use a metacharacter to serve as a substitute.

Three metacharacters that work with this command include:
  - **Period (.):** Specifies the current and all nested folders.
  - **Forward Slash (/):** Specifies the entire filesystem.
  - **Tilde (~):** Specifies the active user's home directory.

----

==== Expressions ====

This specifies how we want to match what we are looking for. 

**Most common:** ''-name'' (searches for the name you provide of a file or folder).

<code>
find / -name file.txt   # specify exact name
find / -name 'file1*'   # use search patterns
find / -name '*.txt'    # use search patterns for extentions
find / -iname 'FILE.txt # use iname for a case-INsensitive search
</code>

Other expressions to use...

----

==== Find Files by Type ====

Use the ''-type'' expression. The most common is "f" for file but the others are just as easy:

^  Type  ^ Description  ^
|  f  | regular file |
|  d  | directory |
|  l  | symbolic link |
|  c  | character device |
|  b  | block device |
|  p  | named pipe (FIFO) |
|  s  | socket |

**Examples: **

<code>
find . -type d               # find only/all directories, recursive
find . -type f               # find only/all files, recursive
find . -type f -name '*.txt' # find only/all files named with txt extension
</code>

----

==== Find Files by Size ====

Use the ''-size'' expression. All units are rounded up (this is tricky!), for example, 1M = 1048576c but:
  * ''-size -1M'' will find only empty files (because anything less that 1 is 0, therefore this will match only those files less than 1, which is 0M).
  * ''-size -1048576c'' will find files from 0 to 1,048,575 bytes (i.e. 0 to one byte below 1M).

^  Suffix  ^ Description  ^
|  b  | blocks (512 bytes), default |
|  c  | bytes |
|  k  | kilobytes |
|  M  | Megabytes |
|  G  | Gigabytes |

^  Prefix  ^ Description  ^
|  +  | greater than |
|  -  | less than |

**Example:** 

<code>
find . -type f -size +50c  # find all files larger than 50 bytes
find . -type f -size 510c  # find all files exactly 510 byes
</code>

----

==== Find Files by Owner ====

Use the ''--user'' expression and provide the username or user ID (uid). Examples:

<code>find . -type f -user greg</code>

----

==== Find Files by Perms ====

Use the ''-perm'' expression. There are three ways to specify perm mode: 
  - **No prefix:** find exact permissions
  - **Prefix of '-':** find "at least" permissions (not exact)
  - **Prefix of '/':** find permission in either owner, group, OR other

**Examples:**

<code>
find . -type f -perm 664 
# find files with exactly 644 perms in current dir and all subdirs

find . -type f -perm -664
# find files with "at least" 644 perms (and more)

find . -type f -perm /222
# find files writeable by somebody (owner, group, OR other)

find . -type f -perm /220
# find files writeable by EITHER owner OR group (but no one else)

find . -type f -perm -220
# find files writeable by BOTH owner AND group (but no one else)

find / -perm /4000 -type f -exec ls -ld {} \; 2>/dev/null
# This will find files with the SUID bit set.
# -l long listing format
# -d list directory names, not contents
</code>

----

==== Find Files by Timestamps ====

You can find files by modification, access, or change in timestamps.

Three timestamps for **DAYS** (24-hour periods): 

^  Type  ^ Description  ^
|  atime  | shows when the file was last accessed (e.g., read) |
|  mtime  | shows when the file contents were last modified |
|  ctime  | shows when metadata was last changed (including content modification) |

Three timestamps for **MINUTES** (60-second periods)

^  Type  ^ Description  ^
|  amin  | file was last accessed (e.g., read) |
|  mmin  | file contents were last modified |
|  cmin  | file metadata was last changed (including content modification) |

^  Prefix  ^ Description  ^
|  +  | greater than |
|  -  | less than |

**Note:** Any fractional part of the time period is ignored. Therefore ''-atime +1'' will find files accessed TWO days ago or longer (because files accessed today, or within the last 23.99 hours, can be found with ''atime 0''). 

Examples: 

<code>
find . -type f -mtime -10
# find all files modified less than 10 days ago
# find all files less than 10 days old

find . -type f -mtime +10
# find all files modified more than 10 days ago
# find all files older than 10 days old

find . -type f -mtime 0
# find all files modified today
</code>

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