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Linux Shell Commands - 03 Search & Pack Files

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This post is Part Three of the summary of some common Linux Shell Commands. The commands we are going to use today are: find, locate, gzip, tar.


Searching Files: find


Usage

find <PATH> <Expression>

Here <Expression> contains 4 types:

  • options
  • tests (T / F)
  • actions
  • operators

e.g. find /etc -size +100k

Find files that size > 100k, under the directory /etc. Note that:

  • +n: ≥ n

  • n: = n

  • -n: ≤ n


Wildcard Chars

Four Common Types

  • *: Match 0, or multiple chars

  • ?: Match any one char

  • [STRING]: Match any char in the string.

    • e.g. [a-z0-9] matches lowercase letters and digits
    • Note that [! STRING]means match any other chars except ones after !

  • \: escape


Using Wildcard with find:

  • -iname: ignore cases

  • find /usr -name "te*sh": find all files types under /usr, starting with te, ending with sh.

  • -path & -wholename: find paths

  • find /usr -wholename /usr/bin: find bin under /usr directory. Note that the 2 directories, path prefix must be the same, and must be whole paths.

  • -regex & -iregex


Symbolic Links (Soft Links):

  • -lname & -ilname: Test. Check if a file is a symbolic link.

  • find /usr/bin -lname "*python3*" : find soft links that contain python3 in the filenames.


Hard Links:

  • find /usr -samefile file1: Use -samefile to find all hard links of file1.

  • find /usr -inum <inode>: Each inode has a unique number, but hard links have the same inode.

  • find /usr -links 3: find files that have 3 hard links.


Time

Each file has three timestamps:

  • Access (-atime n, -amin n)
  • Change (-ctime n, -cmin n) : Change file status
  • Modify (-mtime n, -mmin n) : Edit file content

e.g. Modify time between 5 mins and 24 hours before.

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find /usr -mtime 0 -mmin +5

Size

-size n[bckwMG]: n is the number (+, -)

  • b: Block

  • c: Char

  • k: KB

  • w: Number of 2-byte chars

  • M: MB

  • G: GB


Type

-type [dfl]:

  • d: Dir.

  • f: File

  • l: Links


e.g. Normal file, size > 30k.

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sudo find /etc -type f size +30k

Owner

  • -user <NAME>
  • -group <GROUP>
  • -uid n & -gid n

e.g. find /usr -uid 0: (Root’s UID is 0)


File Mode Bits

  • -readable & -writeable & -executable

e.g. Check the files under /etc that can be executed by current user, ending with a.

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find /etc -executable -name "*a"

-Exec

Must have {} and \;.


List detailed info of the files

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find /usr -type f -exec ls -l {} \;

Delete all files that are modified more than 14 days ago.

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find /usr -type f -mtime +14 -exec rm {} \;

Delete .log files, and press y to confirm, before each deletion.

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find /usr -name "*.log" -ok rm {} \;

Find files start with passwd, and contains the word root.

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find /etc -name "passwd*" -exec grep "root" {} \;

More Examples

Find all files (size > 12k) under /etc, copy to /home/backup, with original directories (-rp --parents):

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sudo find /etc -type f -size +12k -exec cp -rp --parents {} /home/backup \;

Searching Files: locate

locate is to find results in a database that contains all files and directories in the system. The database isn’t updated in real time. To update, use:

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sudo updatedb

Usage:

  • locate /usr/bin/python

  • locate --basename hello: filename (not dir. name) contains hello


Packing Files: gzip and tar

Usually we need to first pack the files using tar, then zip the .tar files. Because many compressors in Linux can only compress one file each time, so it’s better to compress a packed file.

gzip: .gz

To zip a file: gzip <FILE>

To unzip a file: gunzip <FILE>


tar: .tar

Usage: tar <OPTION> <FILE>

  • -z & --gzip: Use gzip to compress

  • -c: Create

  • -v: detailed process

  • -f: filename

  • -x: unpack

  • -r: Append to end of file


  • e.g. Pack & zip: 

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    tar -zcvf /etc/hello.tar.gz /home/hello1 /home/hello2

  • e.g. Unpack & unzip: 

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    tar -zxvf /etc/hello.tar.gz /home