oam/knowledge base/find.md

# Find

## TL;DR

```shell
# Change the permissions of all files and directories in the current directory,
# recursively.
find . -type d -exec chmod 755 {} +
find . -type f -exec chmod 644 {} +

# Change the ownership of all files and directories owned by a specific user or
# group, recursively.
find . -type d -user harry -exec chown daisy {} +
find . -type f -group users -exec chown :admin {} +

# Delete all empty files and directories in the 'Documents' directory.
find Documents -empty -delete               # recursively
find Documents -maxdepth 1 -empty -delete   # non recursively

# Get the extensions of all files larger than 1MB.
find . -type f -size +1M -exec basename {} \; | sed 's|.*\.||' | sort -u

# Find files last accessed exactly 5 hour ago.
find . -type f -amin 300
find . -type f -atime 5h

# Find files last modified in the last hour.
find . -type f -mmin -60
find . -type f -mtime -1h

# Find files created more than 2 days ago.
find . -type f -ctime +2

# Find all empty directories in a git repository that are not from git itself.
find path/to/repo -type d -empty -not -path "./.git/*"

# Find broken symlinks in the given directories, recursively.
find dir/1 dir/n -type l -exec test ! -e {} \; -print
find dir/1 dir/n -xtype l   # gnu find only

# Sort files by name, in numeric order, regardless of the directory they are in.
find . -type f -o -type l \
  | awk 'BEGIN {FS="/"; OFS="|"} {print $NF,$0}' \
  | sort --field-separator '|' --numeric-sort \
  | cut -d '|' -f2

# Print quoted file paths.
# %p is for path.
find . -type f -printf '%p\n'

# Sort files by size.
# %s is for size, %p is for path.
find . -type f -printf '%s %p\n' | sort -nr | head -50

# Find files which are executable but not readable.
find /sbin /usr/sbin -executable -not -readable -print

# Find files which are writable by either their owner or their group.
find . -perm /220
find . -perm /u+w,g+w
find . -perm /u=w,g=w

# Find files which are writable by both their owner and their group.
find . -perm -220
find . -perm -g+w,u+w

# Record set-user-ID files and directories into '/root/suid.txt', and large
# files into 'big-files.txt'
find / \
  \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \
  \( -size +100M -fprintf big-files.txt '%-10s %p\n' \)
```

## Time specifications

Primaries used to check the difference between the file last access, creation or modification time and the time `find` was started.

All time specification primaries take a numeric argument, and allow the number to be preceded by a plus sign (`+`) or a minus sign (`-`).  
A preceding plus sign means **more than `n`**, a preceding minus sign means **less than `n`** and neither means **exactly `n`**.

Accepted time information:

- `a` for the file's last access time
- `c` for the time of last change of file status information (creation)
- `m` for the file's last modification time
- `B` for the file's inode creation time
  
With the `-Xmin` form, times are rounded up to the next full **minute**. This is the same as using `-Xtime Nm`.

With the `-Xtime` form, times depend on the given unit; if no unit is given, it defaults to full 24 hours periods (days).  
Accepted units:

- `s` for seconds
- `m` for minutes (60 seconds)
- `h` for hours (60 minutes)
- `d` for days (24 hours)
- `w` for weeks (7 days)

Any number of units may be combined in one `-Xtime` argument.

with the `-newerXY file` form, `find` checks if `file` has a more recent last access time (X=a), inode creation time (X=B), change time (X=c), or modification time (X=m) than the last access time (Y=a), inode creation time (Y=B), change time (Y=c), or modification time (Y=m).  
If Y=t, `file` is interpreted as a direct date specification of the form understood by `cvs`. Also, `-newermm` is the same as `-newer`.

```shell
# Find files last accessed exactly 5 minutes ago.
find /dir -amin 5
find /dir -atime 300s
find /dir -atime 5m

# Find files last accessed in the last 3 days.
find /dir -atime -3
find /dir -atime -3d

# Find files created in the last 1.5 hour.
find /dir -cmin -90
find /dir -ctime -1h30m

# Find files created more than 4 days ago.
find /dir -ctime +4

# Find files modified less than 30 minutes ago.
find /dir -mmin -30
find /dir -mtime -30m
find /dir -mtime -.5h   # gnu find only

# Find files modified exactly 2 days ago.
find /dir -mtime 2
find /dir -mtime 48h

# Find files modified more than 4 weeks ago.
find /dir -mtime +28
find /dir -mtime +4w

# Find all files whose inode change time is more recent than the current time
# minus one minute.
find / -newerct '1 minute ago'

# Find files owned by 'wnj' that are newer than 'file.txt'.
find / -newer file.txt -user wnj -print
```

## Gotchas

- in GNU's `find` the path parameter defaults to the current directory and can be avoided

  ```shell
  # Delete all empty folders in the current directory only.
  find -maxdepth 1 -empty -delete
  ```

- GNU's `find` also understands fractional time specifications:

  ```shell
  # Find files modified in the last 1 hour and 30 minutes.
  find -mtime 1.5h
  ```

## Further readings

- [How can I find broken symlinks?]
- [find . -type f -exec chmod 644 {} ;]
- [how to output file names surrounded with quotes in SINGLE line?]

[find . -type f -exec chmod 644 {} ;]: https://stackoverflow.com/questions/19737525/find-type-f-exec-chmod-644#22083532
[how can i find broken symlinks?]: https://unix.stackexchange.com/questions/34248/how-can-i-find-broken-symlinks
[how to output file names surrounded with quotes in single line?]: https://stackoverflow.com/questions/6041596/how-to-output-file-names-surrounded-with-quotes-in-single-line#15137696