added find command

2025-11-09 12:45:21 +03:30
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+# `find` — quick reference & practical documentation
+
+This is a compact, practical reference for the Unix/Linux `find` command aimed at DevOps engineers and system administrators. It covers common options, tests, actions, operators, examples (safe and practical) and performance tips.
+
+---
+
+# Synopsis
+
+```
+find [path...] [expression]
+```
+
+If no `path` is given, `find` searches the current directory (`.`). `expression` is evaluated left-to-right and can contain tests, actions and operators.
+
+---
+
+# Basic behaviour
+
+* `find` walks directory trees recursively by default.
+* An *expression* evaluates to true/false; when true, the default action `-print` (or whatever action is specified) is executed.
+* You can control traversal order with `-depth` and `-maxdepth`/`-mindepth`.
+* `-prune` prevents descending into directories.
+
+---
+
+# Common options and switches
+
+* `-H` : follow symbolic links specified on the command line.
+* `-L` : follow all symbolic links.
+* `-P` : never follow symbolic links (default).
+* `-xdev` : don't descend into directories on other filesystems (useful when walking `/`).
+* `-mindepth N` : do not apply tests/actions to files at depth < N.
+* `-maxdepth N` : do not descend past depth N.
+* `-depth` : process directory contents before the directory itself (useful for safe deletes).
+* `-mount` : same as `-xdev` (GNU find).
+
+---
+
+# Common tests (predicates)
+
+* `-name pattern` : match basename with shell globbing (case-sensitive). Pattern uses shell wildcards (`*`, `?`, `[]`).
+* `-iname pattern` : case-insensitive `-name`.
+* `-path pattern` : match the whole path (slash-separated) with shell globbing.
+* `-ipath pattern` : case-insensitive `-path`.
+* `-regex pattern` : match full path with regular expression (syntax differs by `find` implementation; GNU `find` defaults to Emacs regex).
+* `-type c` : file type; `f` = regular file, `d` = directory, `l` = symlink, `c` = character device, `b` = block device, `p` = FIFO, `s` = socket.
+* `-perm mode` : file permission test. Modes:
+
+  * octal: `-perm 0644` (exact)
+  * symbolic: `-perm -u=w` (any of the bits), `-perm /u=w` (any), `-perm -0644` (all bits set)
+  * GNU `find` also accepts `/mode` to mean "any of the bits".
+* `-user name` / `-uid uid` : owner.
+* `-group name` / `-gid gid` : group.
+* `-size n[cwbk]` : file size; default 512-byte blocks for some `find` versions; most use 1K blocks for `k`. GNU `find` suffixes:
+
+  * `c` = bytes
+  * `k` = kilobytes
+  * `M` = megabytes
+  * `G` = gigabytes
+  * `+n` = greater than n, `-n` = less than n, `n` = exactly n
+* `-mtime n` / `-atime n` / `-ctime n` : modified / accessed / changed time in 24-hour periods; `-mtime +7` older than 7 days, `-mtime -7` less than 7 days, `-mtime 7` exactly 7.
+* `-mmin n`, `-amin n`, `-cmin n` : minutes.
+* `-newer file` : newer than file (can be combined with `!` to negate).
+* `-empty` : empty file or directory.
+* `-links n` : number of hard links.
+* `-readable` / `-writable` / `-executable` : access checks from running user perspective.
+
+---
+
+# Common actions
+
+* `-print` : print path (often default; some implementations require explicit `-print` with complex expressions).
+* `-print0` : print paths separated by NUL (safe with whitespace/newlines).
+* `-ls` : list file using `ls -dils` style.
+* `-exec command {} \;` : run `command` once per matched file. `{}` is replaced by the current path. The `\;` terminator must be escaped or quoted.
+* `-exec command {} +` : optimized form; appends multiple matches to command arguments like `xargs` (more efficient).
+* `-ok command {} \;` : like `-exec` but prompts the user before each execution.
+* `-delete` : delete matched files/directories (be careful; obeys ordering and `-depth`).
+* `-prune` : exclude directory from descent (returns true; often used with `-o`).
+* `-quit` : stop after first match (very efficient when used with `-print`).
+* `-mindepth N`, `-maxdepth N` already described; they behave like tests.
+
+---
+
+# Operator precedence (GNU `find` style)
+
+* Parentheses `(` `)` group expressions. They must be escaped or quoted: `\( ... \)` or `'(' ... ')'`.
+* `!` or `-not` : logical NOT (unary).
+* `-a` or implicit concatenation : logical AND.
+* `-o` or `-or` : logical OR.
+* Evaluation is left-to-right; `-a` has higher precedence than `-o`. Use parentheses to be explicit.
+* Common pitfall: mixing `-prune` and `-o` requires careful grouping:
+  Example pattern to exclude `dir`:
+
+  ```
+  find . -path ./dir -prune -o -print
+  ```
+
+  This means: if path is `./dir` prune it (and `-prune` returns true) otherwise (`-o`) `-print`.
+
+---
+
+# Typical practical examples
+
+Search examples assume `bash` shell; escape parentheses and semicolons as needed.
+
+1. Find files by name (case-sensitive)
+
+```
+find /var/log -type f -name "syslog*"
+```
+
+2. Case-insensitive:
+
+```
+find /home -type f -iname "*.jpg"
+```
+
+3. Find empty directories:
+
+```
+find /path -type d -empty
+```
+
+4. Delete `*.tmp` files safely (print first, then delete)
+
+```
+find /data -type f -name "*.tmp" -print
+find /data -type f -name "*.tmp" -delete
+```
+
+Or safer with confirmation:
+
+```
+find /data -type f -name "*.tmp" -ok rm {} \;
+```
+
+5. Find and remove files older than 30 days (safe: use `-print` first)
+
+```
+find /var/log -type f -mtime +30 -print
+find /var/log -type f -mtime +30 -exec rm -- {} +
+```
+
+Prefer `-exec ... +` over `-exec ... \;` for efficiency.
+
+6. Remove directories older than 30 days (use `-depth` to ensure files inside are removed first)
+
+```
+find /tmp -depth -type d -mtime +30 -exec rm -rf -- {} +
+```
+
+`-delete` may also be used but beware of ordering; `-depth` ensures children processed before parent.
+
+7. Find files with spaces and handle them safely:
+
+```
+find /srv -type f -name "*.conf" -print0 | xargs -0 grep -H "pattern"
+```
+
+8. Find files larger than 100 MiB:
+
+```
+find / -type f -size +100M -print
+```
+
+9. Find files newer than a reference file:
+
+```
+find /web -type f -newer /tmp/deploy_marker -print
+```
+
+10. Find and run a command on many files (batching):
+
+```
+find /data -type f -name "*.log" -exec gzip -- {} +
+```
+
+11. Exclude a directory (`dir_to_skip`) while listing everything else:
+
+```
+find . -path "./dir_to_skip" -prune -o -print
+```
+
+12. Only search one level (non-recursive):
+
+```
+find . -maxdepth 1 -type f -print
+```
+
+13. Find broken symlinks:
+
+```
+find / -xtype l -print
+```
+
+Note: `-xtype` tests the target type; `-L` changes behavior of `-type`.
+
+14. Use `-printf` to customize output (GNU find):
+
+```
+find . -type f -printf "%p\t%k KB\t%TY-%Tm-%Td %TH:%TM:%TS\n"
+```
+
+`-printf` supports format sequences (`%p` path, `%s` bytes, `%k` KB blocks, `%TY` year, ...). Exact spec depends on implementation (GNU has extensive options).
+
+15. Stop at first match (fast):
+
+```
+find /usr -type f -name "passwd" -print -quit
+```
+
+16. Find files modified within last 15 minutes:
+
+```
+find /var -type f -mmin -15
+```
+
+---
+
+# Safe deletion checklist
+
+* Always `-print` or `-ls` first to verify matches.
+* Prefer `-exec rm -- {} +` or use `-delete` with `-depth` if required.
+* Watch out for `-maxdepth`/`-mindepth` to avoid accidental top-level deletions.
+* Use `-print0` + `xargs -0` when passing to other utilities.
+* Consider using `-ok` for destructive changes in interactive contexts.
+
+---
+
+# Performance & scalability tips
+
+* Limit scope: pass explicit starting paths instead of `.` or `/` when possible.
+* Use `-maxdepth` and `-mindepth` to reduce traversal.
+* Use `-xdev` to avoid crossing filesystem boundaries (speeds up root scans).
+* Combine fast tests early (e.g., `-type f -name "*.log"` rather than `-name` alone) because find evaluates left-to-right; short-circuiting happens when possible.
+* Prefer `-exec ... +` to `-exec ... \;` to reduce process spawn overhead.
+* Use `-prune` to skip large tree branches that aren’t needed.
+* On very large trees consider tools optimized for indexing (e.g., `locate` / `mlocate`, `fd`, or ripgrep for content search). `find` is always consistent but traverses the disk each run.
+
+---
+
+# Portability notes
+
+* Behavior, available tests/actions and argument formats vary slightly between implementations (GNU `find` vs BSD `find` vs BusyBox). Examples above assume GNU `find` when using `-printf`, `-delete`, `-quit` or suffixes like `M`/`G` for sizes.
+* When writing scripts for mixed environments, try to stick to portable tests: `-name`, `-type`, `-mtime`, `-print`, `-exec ... \;`. Check `/usr/bin/find --version` or `man find` on target hosts.
+
+---
+
+# Gotchas & common pitfalls
+
+* Shell globbing vs `find` globbing: `-name "*.txt"` is matched by `find` and must be quoted to prevent shell expansion.
+* `-perm` exact vs any-bit semantics differ across versions; test on target system.
+* `-regex` matches the whole path, not just basename; regex dialect differs (use `-regextype posix-extended` on GNU `find` to set type).
+* `-delete` will fail if used before tests that select children (order matters). Use `-depth` or test ordering appropriately.
+* Beware of running `find` as root with `-exec rm -rf {}` — very dangerous if expression is wrong. Always verify output.
+* `-maxdepth`/`-mindepth` may not be supported in very old `find` implementations.
+
+---
+
+# Exit status
+
+* `0` : at least one match and command completed successfully.
+* `1` : no matches were found (behavior can vary).
+* `>1` : an error occurred (e.g., permission errors or malformed expression).
+  Note: exact meanings can depend on implementation.
+
+---
+
+# Useful combinations
+
+* Find files and preserve relative paths for tar:
+
+```
+cd /path && find . -type f -name "*.conf" -print0 | tar --null -T - -czf confs.tar.gz
+```
+
+* Find and change ownership or permissions:
+
+```
+find /srv/www -type f -name "*.php" -exec chown www-data:www-data {} +
+find /srv/www -type d -exec chmod 755 {} +
+```
+
+* Search content in matched files:
+
+```
+find /app -type f -name "*.py" -print0 | xargs -0 grep -n "TODO"
+```
+
+---
+
+# Related commands/tools
+
+* `locate` / `mlocate` : fast filename lookup (uses database).
+* `fd` : simpler, faster user-friendly alternative to `find` (not always installed).
+* `xargs` : pass batches of arguments to commands (careful with spaces; use `-print0` + `xargs -0`).
+* `stat` : detailed file metadata for a single file.
+* `rm`, `tar`, `gzip`, `chown`, `chmod`, `rsync` : commonly used alongside `find`.
+
+---
+
+# Quick cheatsheet (most-used patterns)
+
+* Find files by name: `find /path -type f -name "pattern"`
+* Case-insensitive: `-iname`
+* Size bigger than 100M: `-size +100M`
+* Modified > 7 days: `-mtime +7`
+* Delete old files: `find /dir -type f -mtime +30 -exec rm -- {} +`
+* Print NUL-separated: `-print0`
+* Safe prune: `find . -path ./skip -prune -o -print`
+* Batch exec: `-exec cmd {} +`
+* Stop on first: `-print -quit`