Finding Files¶

The bulk of this file is notes on the find command.
Before that, some other commands to find files.

Table of Contents¶

tree
ls
which
The find Command
Quick Overview of File Timestamps
tl;dr: Examples
Executing commands on found file(s)
find Options
Testing Files with find
- Users and Groups
- Permissions
Testing Timestamps of Files with find
- Other Tests That Use Timestamps
Performing Actions on Files Using find
Operators For Multiple Conditions
- Searching with and/or Examples
Permission Searching
- Searching for Permissions Examples
Timestamps Explained

`tree`¶

tree -I '.git' - Tree view of current directory and subdirectories.
- -I(gnore) the .git directory.

`ls`¶

ls -I '.git'          # List current directory, -I(gnore) .git/
ls -I '.git' *.md     # List all markdown files in current directory
ls -I '.git' **/*.md  # List all markdown files, recursively (**). Requires `set -o globstar` in bash.

`which`¶

The which command will show you where the executable binary is for a command or script:

which bash
# /usr/bin/bash

The `find` Command¶

The king: find. Has 5 "main" arguments.
-H, -L, -P, -D and -O must appear before the first path name if used.
You can specify the type of regex used with -regextype (find -regextype help)

Quick Overview of File Timestamps¶

Attribute	Meaning
`atime`	file *Accessed* time
`mtime`	file's *contents* *Modified* time
`ctime`	file's *metadata OR contents* *Changed* time

stat {file} will show all three of {file}'s timestamps.
Modification Time: ls -lt will list files with their modification times.
Access Time: Use ls --time=atime -lt to list files with access times.
Change Time: Use ls --time=ctime -lt to list files with change times.

tl;dr: Examples¶

Examples start on line 1147 of man find ¶

Skipping directories (Omitting directories) with `-prune`¶

The -prune option tells find: "if the file is a directory, don't descend into it."
This allows you to skip over the contents of a specific directory.

Skip directories with find:

To SKIP a directory and print all other files found:
```
find . -path ./src/emacs -prune -o -print  # skip the ./src/emacs dir
find . -name '.git' -prune -o -print       # skip the .git dir
```
So, here, we're using find to specifically search for the directory we want to skip, then using -prune to say "don't descend into this directory."
Then, we're using an OR operator (-o) to -print any files that don't match the pattern.

Skip the contents of any .git directory, and search for *.py files

find . -path ".git" -prune -o -path "./*.py" -print
find . -path ".git" -prune -o -name "*.py" -print

Exclude multiple directories by using the OR operator -o inside escaped parentheses: 
```
find . -type d $ -path ./dir1 -o -path ./dir2 -o -path ./dir3 $ -prune -o -name '*.txt' -print
```
- This evaluates everything in the parentheses first, and then does a -prune on all the directories found there. Then, it says -o -name '*.txt' -print (or, with file extension .txt, print the output).

If `-prune` doesn't work, use an Operator instead:¶

Use the -not operator:

find -name "*.md" -not -path "./directory/*"

Finding files that match multiple conditions¶

Check the Operators for Multiple Conditions section for more notes on the operators.

Searching files by age¶

Search for files in your home directory that've been modified in the last 24 hours:

find $HOME -mtime 0

Executing commands on found file(s)¶

Executing a command for each file found¶

Run cat on target.md if it is found:

find . -name 'target.md' -exec cat '{}' ';'

The braces `{}` and semicolon `;` can either be quoted or escaped.¶

Grep inside Found Files¶

find . -name 'target.md' -exec grep -i 'tar.gz' '{}' ';'

This uses grep to find the word tar.gz inside the found files.

Run my_script on every file in or below the current directory:

find . -type f -exec my_script '{}' \;

Executing a command on all files simultaneously¶

Pass all files to my_script as arguments:

find . -type f -exec my_script '{}' +

'{}' expands to the names of the file(s) that are found with find.
+: Tell find to pass all files to my_script as arguments.
- This is different than using ';', which passes the found file to exec one at a time.
- More efficient than ; in this case, which would invoke the script once per file.

Searching files by permissions¶

Note: the `-perm` argument supports both octal notation and symbolic notation (`u=x`, '755' etc)¶

Overview:
Examples of checking for files with owner write and group write permissions:

find . -perm 220       # Match if ONLY the given permissions are there. (exact match)  
find . -perm -220      # Match if given perms are there. Can have more perms. (match if perms exist)  
find . -perm /220      # Matches if ANY of the given permissions are there.  
find . -readable       # Checks that 'r' is present for current user  
find . -writable       # Checks that 'w' is present for current user  
find . -executable     # Checks that 'x' is present for current user  
find . \! -executable  # Checks that 'x' is absent for current user

The symbolic notation equivalents of those examples:

find . -perm g=w,o=w    # Must have only the permissions given.  
find . -perm -g=w,o=w   # All given permissions must exist. May have other perms.  
find . -perm /g=w,o=w   # At least one of the permissions must exist.

Conditional Search Examples:¶

Search for files in /sbin that are executable but not readable:

find /sbin /usr/sbin -executable \! -readable -print

Search for files in the current directory with read and write permission for their owner, and group, but other users can read but not write to.
```
find . -perm 664  
```

`find` Options¶

Global Options¶

-depth: Process each directory's contents before the directory itself.
- -d: POSIX-compatible -depth
- The -delete action also implies -depth.
-ignore_readdir_race: find won't give an error message when it fails to stat a file.
- -noignore_readdir_race: Turns off the effect of -ignore_readdir_race.
-maxdepth levels: Descend at most levels levels of directories below the starting points.
-mindepth levels: Don't apply any tests or actions at levels less than levels.
-mount: Don't descend directories on other filesystems.
- An alternate name for -xdev, for compatibility with some other versions of find.
-noleaf: Don't optimize by assuming that directories contain 2 fewer subdirectories than their hard link count (. and ..).
- This option is needed when searching filesystems that don't follow the Unix directory-link convention, like CD-ROM or MS-DOS filesystems or AFS volume mount points.
-path pattern: File name matches shell pattern pattern.
- The metacharacters do not treat / or . specially; so, for example,
```
find . -path "./sr*sc"  
```
  will print an entry for a directory called ./src/misc.
-follow: Deprecated - use -L instead
-help / --help: help.

Change How `find` Handles Symbolic Links¶

The first 3 deal with symbolic links:

-P: Never follow symbolic links. (default)
-L: Follow symbolic links
-H: Don't follow symbolic links, except while processing the command line arguments.

Get Diagnostic Information from `find`¶

-D debugopts: Print diagnostic information;
- use to diagnose problems with why find is not doing what you want.
- debugopts should be comma separated.
- find -D help for full list of options.
  - exec: info on -exec, -execdir, -ok, & -okdir
  - all: enables all of the other debug options (except help)

`find` Query Optimization¶

-Olevel: Enables query optimisation. Should make find run faster or consume less resources.
- -O0: Same as -O1
- -O1: Default.
- -O2 and -O3: More optimized stuff, rtfm 🙃

Testing Files with `find`¶

There are a ton of tests available to find.

Some tests, allow comparison between the file currently
being examined and some reference file specified on the command line.
( for example -newerXY and -samefile, -cnewer, -anewer, -newer ).
See Timestamps Explained.

A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used)

+n: for greater than n
-n: for less than n
n: for exactly n
-regex pattern: File name matches regular expression pattern.
- -iregex pattern: Like -regex, but the match is case insensitive.
-path pattern: File name matches shell pattern pattern.
- -ipath pattern: Like -path but the match is case insensitive.
- -iwholename pattern: See -ipath. This alternative is less portable than -ipath.
- -wholename pattern: See -path. This alternative is less portable than -path.
-name pattern: Base of file name (the path with the leading directories removed) matches shell pattern pattern.
- The file names considered for a match with -name will never include a slash,
  - -name a/b will never match anything
  - (you probably need to use -path instead).
- -iname pattern: Like -name, but the match is case insensitive.
- -lname pattern: File is a symbolic link whose contents match shell pattern pattern.
- -ilname pattern: Like -lname, but the match is case insensitive.
-type c: File is of type c:
- b: block (buffered) special
- c: character (unbuffered) special
- d: directory
- p: named pipe (FIFO)
- f: regular file
- l: symbolic link
  - this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken.
    - If you want to search for symbolic links when -L is in effect, use -xtype.
- s: socket
- D: door (Solaris)
-xtype c: The same as -type unless the file is a symbolic link.

Users and Groups¶

-user uname: File is owned by user uname (numeric user ID allowed).
-nogroup: No group corresponds to file's numeric group ID.
-nouser: No user corresponds to file's numeric user ID.
-gid n: File's numeric group ID is less than, more than or exactly n.
-group gname: File belongs to group gname (numeric group ID allowed).
-uid n: File's numeric user ID is less than, more than or exactly n.

Permissions¶

-perm mode: File's permission bits are exactly mode (octal or symbolic).
-perm -mode: All of the permission bits mode are set for the file.
-perm /mode: Any of the permission bits mode are set for the file.

-samefile name: File refers to the same inode as name.
-links n: File has less than, more than or exactly n hard links.
-inum n: File has inode number smaller than, greater than or exactly n.
-size n[cwbkMG]: File uses less than, more than or exactly n units of space, rounding up.
- b: for 512-byte blocks (this is the default if no suffix is used)
- c: for bytes
- w: for two-byte words
- k: for kibibytes (KiB, units of 1024 bytes)
- M: for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes)
- G: for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes)
-context pattern: (SELinux only) Security context of the file matches glob pattern.

-false: Always false.
-true: Always true.
-empty: File is empty and is either a regular file or a directory.
-readable: Matches files which are readable by the current user.
-writable: Matches files which are writable by the current user.
-executable: Matches files which are executable and directories which are searchable by the current user.
-fstype type: File is on a filesystem of type type.
- An incomplete list: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K
- You can use -printf with the %F directive to see the types of your filesystems.

Testing Timestamps of Files with `find`¶

For testing the timestamps on files:

-daystart: Measure times from the beginning of today rather than from 24 hours ago.
(for -amin, -atime, -cmin, -ctime, -mmin, and -mtime)

Option	Timestamp Tested
`-amin ±n`	Access Time in Minutes
`-atime ±n`	Access Time in Days
`-cmin ±n`	Status Change Time in Minutes
`-ctime ±n`	Status Change Time in Days
`-mmin ±n`	Modification Time in Minutes
`-mtime ±n`	Modification time in Days
`-cnewer reference`	Status Change Time of the current file is more recent than`reference` file
`-anewer reference`	Access Time of the current file is more recent than `reference` file

±: Plus or Minus - n can be positive or negative.
- -amin +5: Finds files accessed MORE than 5 minutes ago.
- -amin -5: Finds files accessed LESS than 5 minutes ago.
- -amin 5: Finds files accessed EXACTLY 5 minutes ago.

Other Tests That Use Timestamps¶

-used n: File was last accessed less than, more than or exactly n days after its status was last changed.
-newer reference: Time of the last data modification of the current file is more recent than that of the last data modification of the reference file.
-anewer reference: Time of the last access of the current file is more recent than that of the last data modification of the reference file.
-cnewer reference: Time of the last status change of the current file is more recent than
that of the last data modification of the reference file.
-newerXY reference: Succeeds if timestamp X of the file being "found" is newer than timestamp Y of the file reference.
- The letters X and Y can be any of the following letters:
  - a: The access time of the file reference
  - B: The birth time of the file reference
  - c: The inode status change time of reference
  - m: The modification time of the file reference
  - t: reference is interpreted directly as a time

Performing Actions on Files Using `find`¶

There are several "actions" you can specify when using find.
These actions will determine how the found files will be handled.
- -print (default): Outputs the file names separated by newlines. - -print0: Outputs the file names separated by NULL bytes.
- This is generally considered safer since funky filenames won't break things.
- -printf <format>: Format print. Doesn't add a newline like -print.
- Useful for listing extended data about the file (atime, mtime, users, etc.).
- Field widths/precision same as printf() in C.
- Many of the fields are printed as %s rather than %d - The - flag does work (it forces fields to be left-aligned).
- -fprint <file>: Same as -print, but instead output to <file> - -fprint0 <file>: Same as -print0, but instead output to <file> - -fprintf <file>: Same as -printf, but instead output to <file>

-ls: List found files just like ls -dils.
-fls <file>: Like -ls but write to <file>, just like -fprint.
-prune: If the file is a directory, don't descend into it.
- If -depth is specified, -prune is ignored.
-delete: Delete found files.
- This implies -depth. So using -prune with -delete is not effective.
-exec {} \;: Execute a command on the file.
- The '{}' expands to the current filename. This is optional.
-execdir {} \;: Like -exec, but the command run from the directory containing the file.
-ok command \;: Like -exec but asks the user first.
-okdir command \;: Like -execdir but asks the user first.
-quit: Just quits.

-exec command {} +: Like -exec but runs the specified command on all of the files as arguments to the one command.
- Works by appending each selected file name at the end.
- The number of invocations of the command will be much less than the number of matched files.
-execdir command {} +: Same as -execdir, but with -exec cmd {} +

Using -prune to skip the directory ./src/emacs and print all other files found:

find . -path ./src/emacs -prune -o -print

Operators For Multiple Conditions¶

-and / -a / expr1 expr2
- Match multiple conditions
  - -a and expr1 expr2 are POSIX-compliant, -and is NOT.
- Putting the expressions next to each other without this operator will have the same effect.
```
find . -name '*.py' -and -path './sr*py*'
find . -name '*.py' -a -path './sr*py*'  # Same thing. POSIX-compliant
find . -name '*.py' -path './sr*py*'     # Same thing. POSIX-compliant
```
- This will match any .py files in ./src/python.
-not / \!
- Using -not is one way to exclude certain files
  - This is not POSIX-compliant.
- A bang ! can be used. It needs to be either escaped (\!) or quoted ('!').
  - This is POSIX-compliant.
- If whatever follows -not or \! evaluates to true, it won't match.
```
find . -not -type d
```
- This will match everything that isn't itself a directory.
-or / -o
- Or; Match files with either expr1 or expr2
  - -or is not POSIX-compliant.
  - -o is POSIX-compliant.
```
find . -type d -o -name '*.txt'
```
  - This will match any directory and any .txt file.
Parentheses: Force precedence. Anything in parentheses will be evaluated first.
- Parentheses either need to be escaped or quoted:
```
find . $ -path "./my*pt.py" $ -path './some*path'
find . '( -path "./my*pt.py" )' -path './some*path'
```

Searching with and/or Examples¶

find . -name '*.py' -and -path './sr*py*'   # This will match any `.py` files in `./src/python`.
find . -name '*.py' -a -path './sr*py*'  # Same thing. POSIX-compliant
find . -name '*.py' -path './sr*py*'     # Same thing. POSIX-compliant

find . -type d -o -name '*.txt'             # This will match any directory and any `.txt` file.

find . -not -type d                         # Matches everything that's not a directory

Permission Searching¶

There are four main ways to search for permissions.
One way is to use these:

find . -readable        # Readable by Current User
find . -writable        # Writable by Current User
find . -executable      # Executable by Current User
find . \! -readable     # NOT Readable by Current User
find . \! -writable     # NOT Writable by Current User
find . \! -executable   # NOT Executable by Current User

The next three ways use the -perm option.
Using -perm 220, -perm -220, and -perm /220:

find . -perm 220    # Matches if ONLY the given permissions are there (exact matching). 
find . -perm -220   # Matches if given permissions are there. File can have more than 
#                        just the given permissions.  
find . -perm /220   # Matches if ANY of the given permissions are there.

Searching for Permissions Examples¶

Search for files which are executable but not readable.

find /sbin /usr/sbin -executable \! -readable -print

Search for files with read and write permission for their owner, and group, but
which other users can read but not write to.
Match the given permissions EXACTLY.
```
find . -perm 664  
```
Files that have these perms, but also have other permission bits set (for example if
someone can execute the file) will not be matched.

Search for files which have read and write permission for their owner and group, and
other users can read, without caring about any extra permission bits
(for example the executable bit).

Doesn't match perms exactly, only checks if the given permissions are present.

find . -perm -664

This will match a file with 0777 (since 6, 6, and 4 are present).

Search for files which are writable by somebody (their owner, or their group, or any‐
body else).
```
# ANY  
find . -perm /222
```

Search for files which are writable by either their owner or their group.

# ANY  
find . -perm /220  
find . -perm /u+w,g+w  
find . -perm /u=w,g=w

All three of these commands do the same thing, first uses octal, others use symbolic
representation.
The files don't have to be writable by both the owner and group to be matched; either will do.

Search for files which are writable by both their owner and their group.

find . -perm -220  
find . -perm -g+w,u+w

Both these commands do the same thing.

A more elaborate search on permissions.

find . -perm -444 -perm /222 \! -perm /111  
find . -perm -a+r -perm /a+w \! -perm /a+x

These two commands both search for files that are:
1. readable for everybody (-perm -444 or -perm -a+r)
2. have at least one write bit set (-perm /222 or -perm /a+w)
3. but are not ex‐ ecutable for anybody (! -perm /111 or ! -perm /a+x respectively).

Timestamps Explained¶

Access Time (atime):
- This timestamp is updated when the contents of a file are read by any command or application.
Modification Time (mtime):
- This timestamp is updated when the file's content is modified.
- If you edit a file and save changes, its modification time is updated.
- It does not change when the file's metadata (like permissions or ownership) are changed.
Change Time (ctime):
- Often confused with the modification time, the change time is updated when the
  file's metadata or content is changed.
- This includes changes to the file's permissions, ownership, and content.
- It's important to note that ctime is not the creation time of the file.
  - Unix and traditional Linux filesystems do not store the creation time of a file.
stat {file} will show all three of {file}'s timestamps.
Modification Time: ls -lt will list files with their modification times.
Access Time: Use ls --time=atime -lt to list files with access times.
Change Time: Use ls --time=ctime -lt to list files with change times.

"Best Practice": Using `-print0`¶

For "maximum safety," it's recommended to use -print0 when finding files with find.
This requires the use of mapfile instead of read when reading the filenames into an array.
This is used to make sure filenames with spaces or newlines don't break.

E.g., reading a list of files into an array variable:

declare -a FILES
mapfile -d '' -t FILES < <(find . -name '*.md' -print0)

- mapfile: Reads input and indexes it into an array.
- -d '': Use a null character to delimit strings (items in the array). - This is necessary since -print0 separates the filenames with a NULL byte (\0).
- -t: Strips the trailing delimiters (NULL bytes) from files before storing them.
- FILES: The array name.

The -print0 ends each filename with a NULL byte instead of a newline.
So that's why we need to split on \0 (with -d '').

`find` with `-printf`¶

Using -printf allows for some extended control over what, and how, you see output.
The -printf option doesn't add newlines to the end.
This interprets escapes \ and % directives.

This can also be used to format the output by padding with spaces or aligning text.
- E.g., field widths and precision, just like in C.

Escapes and directives can be found at man://find +710.

Printf Directives can be used to find information about the file as well, like permissions, modification times, the files' dirnames, etc..
Some useful directives: - %f: Get the basename of the files. Like running basename $file on each file.
- %s: Size of the file in bytes.

%a will output the file's atime (last accessed time - ctime() in C).
- %Ak (where k is a C strftime format) will print the access time in that format.
%c: Last metadata OR content change time.
%t: Last modification time.
- %Tk (where k is a C strftime format)
%m: Octal permission bits.
%M: Symbolic permission bits.
%b will show the amount of disk space used for the file.
%h: The leading directories of the file's name (all but the actual filename).
And many more.

Finding Files¶

Table of Contents¶

tree¶

ls¶

which¶

The find Command¶