Weight: 4

Candidates should be able to use the basic Linux commands to manage files and directories.

Objectives

  • Copy, move and remove files and directories individually.
  • Copy multiple files and directories recursively.
  • Remove files and directories recursively.
  • Use simple and advanced wildcard specifications in commands.
  • Using find to locate and act on files based on type, size, or time.
  • Usage of tar, cpio and dd.

Terms

  • cp
  • find
  • mkdir
  • mv
  • ls
  • rm
  • rmdir
  • touch
  • tar
  • cpio
  • dd
  • file
  • gzip
  • gunzip
  • bzip2
  • bunzip2
  • xz
  • unxz
  • file globbing

Wildcards and file globbing

File globbing is shell capability which lets you tell things like : - All files - everything which starts with A - all files with 3 letter names which end in A or B or C - ...

To do so you need to know about these characters:

  • * means any string
  • ? means any single character
  • [ABC] matches A, B or C
  • [a-k] matches a, b, c, ..., k (both lower-case and upper-case)
  • [0-9a-z] matches all digits and numbers
  • [!x] means NOT X.

knowing these, you can create your own patterns. For example:

command meaning
rm * delete all files in this directory
ls A*B show all files starting with A ending with B
cp ???.* /tmp Copy all files with 3 characters, then a dot then whatever (even nothing) to /tmp
rmdir [a-z]* remove all empty directories which start with a letter

general commands

listing with ls

ls used to list directories & files. You can provide an absolute or relative path; if omitted the "." will be used as target.

[email protected]:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 16K
-rw-rw-r-- 1 jadi jadi 207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi  29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi  24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi 116 Aug 14 04:44 note_to_self

First field indicates if this is a file (-) or directory (d).

Some common switches are:

  • -l is for long (more info for each file)
  • -1 will print one file per line
  • -t sorts based on modification date
  • -r reverses the search (so -tr is reverse time (newer files at the bottom).

you can mix switches. A famous one is -ltrh (long + human readable sizes + reverse time).

Copy (cp), Move (mv) and Delete (rm)

cp

This will copy files from one place / name to another place / name. If the target is a directory, all sources will be copied there.

cp source destination

A common switch is -r (or -R) which copies recursively (directories and their contents). So for copying a directory called A to /tmp/ you can issue cp -r A /tmp/.

mv

Will move or rename files or directories. It works like cp command. If you are moving a file on the same file system, the inode wont change.

In general:

  • If the target is an existing directory, then all sources are copied into the target
  • If the target directory does not exist, then the source must be only one directory which will be renamed to the target directory.
  • If the target is a file, then the source must be only one file so rename will happen.

These look like "formulas" but they are common sense!

rm

Removes (Deletes) files. You can do this recursively using the -r switch or even prevent it from checking for confirmations using -f (force) switch. So a rm -rf / means delete everything from the file system.

notes

Normally, the cp command will copy a file over an existing copy, if the existing file is writable. On the other hand, the mv will not move or rename a file if the target exists. Although this is highly dependent on your systems configuration. But in all cases you can overcome this using the -f switch.

  • -f (--force) will cause cp to try overwrite the target.
  • -i (--interactive) will ask Y/N question (deleting / overwriting).
  • -b (--backup) will make backups of overwritten files
  • -p will preserve the attributes.

Creating (mkdir) and removing (rmdir) directories

The mkdir command creates directories.

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 16K
-rw-rw-r-- 1 jadi jadi 207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi  29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi  24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi 116 Aug 14 04:44 note_to_self
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ mkdir new_dir
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 20K
-rw-rw-r-- 1 jadi jadi  207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi   29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi   24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi  116 Aug 14 04:44 note_to_self
drwxrwxr-x 2 jadi jadi 4.0K Aug 14 04:57 new_dir

If you want to create a tree of directories, you can use -p switch to tell the mkdir to create the parent directories if needed:

[email protected]:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 20K
-rw-rw-r-- 1 jadi jadi  207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi   29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi   24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi  116 Aug 14 04:44 note_to_self
drwxrwxr-x 2 jadi jadi 4.0K Aug 14 04:57 new_dir
[email protected]:~/lpic1-practice-iso/100/103.3$ mkdir -p 1/2/3 
[email protected]:~/lpic1-practice-iso/100/103.3$ tree
.
├── 1
│   └── 2
│       └── 3
├── data.txt
├── info.txt
├── new_dir
├── note_to_self
└── tasks.txt

If you need to delete a directory the command is rmdir and you can also use the -p for nested removing:

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ rmdir -p 1/2/3
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ rmdir new_dir
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ tree
.
├── data.txt
├── info.txt
├── note_to_self
└── tasks.txt

0 directories, 4 files

If you are using rmdir to remove a directory, it MUST BE EMPTY! Thats why many people use rm -rf directory_name to delete not-empty directory and whatever is in it.

touch

The touch will create an empty file (if it does not exists) or updates the modification date of a file if it already exists. The default time is now but you can specify other times too.

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 16K
-rw-rw-r-- 1 jadi jadi 207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi  29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi  24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi 116 Aug 14 04:44 note_to_self
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ touch new_file
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 16K
-rw-rw-r-- 1 jadi jadi 207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi  29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi  24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi 116 Aug 14 04:44 note_to_self
-rw-rw-r-- 1 jadi jadi   0 Aug 14 05:08 new_file
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ touch note_to_self
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 16K
-rw-rw-r-- 1 jadi jadi 207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi  29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi  24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi   0 Aug 14 05:08 new_file
-rw-rw-r-- 1 jadi jadi 116 Aug 14 05:08 note_to_self

Or you can specify times. It is possible to use -d and give dates or use -t and give a timestamp in the form of [[CC]YY]MMDDhhmm[.ss]

$ touch -t 200908121510.59 file1
$ touch -d 11am file2
$ touch -d "last fortnight" file3
$ touch -d "yesterday 6am" file4
$ touch -d "2 days ago 12:00" file5
$ touch -d "tomorrow 02:00" file6
$ touch -d "5 Nov" file3
$ ls -ltrh file?
-rw-rw-r-- 1 jadi jadi 0 Aug 12  2009 file1
-rw-rw-r-- 1 jadi jadi 0 Aug 12 12:00 file5
-rw-rw-r-- 1 jadi jadi 0 Aug 13 06:00 file4
-rw-rw-r-- 1 jadi jadi 0 Aug 14  2022 file2
-rw-rw-r-- 1 jadi jadi 0 Aug 15  2022 file6
-rw-rw-r-- 1 jadi jadi 0 Nov  5  2022 file3

Oh.. and its possible to use another file's time to set , with switch -r (for --reference)):

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -l /etc/debian_version
-rw-r--r-- 1 root root 13 Aug 22  2021 /etc/debian_version
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ touch -r /etc/debian_version file1
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 20K
-rw-rw-r-- 1 jadi jadi   0 Aug 22  2021 file1

file

To determine the type of a file, you should use file command. It looks into the file and determine its type.

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ file file1
file1: empty
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ file note_to_self
note_to_self: ASCII text
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ file /bin/bash
/bin/bash: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=33a5554034feb2af38e8c75872058883b2988bc5, for GNU/Linux 3.2.0, stripped

-i switch prints the mime format

dd

The dd command copies data from its input to its output (say files or devices). You may use it just like copy:

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ dd if=note_to_self of=new_file
0+1 records in
0+1 records out
116 bytes copied, 0.00141561 s, 81.9 kB/s
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ cat new_file
I will continue learning... and if I get confused, I'll repeat the last section once more till everything is clear!
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$
  • if is Input File
  • of is Output File

But commonly people use it to read / write from block devices. For example this will read all the sectors from the /dev/sdb and will write them to a file namedbackup.dd. Later you can restore this backup by swapping the if and of and write from the backup.dd to /dev/sdb.

# dd if=/dev/sda of=backup.dd bs=4096

or even:

# dd if=/dev/sda2 | gzip > backup.dd.gzip

Another common usage is creating files of specific size:

$ dd if=/dev/zero of=1g.bin bs=1G count=1

or even writing your iso files to a USB disk to have a live bootable USB:

$ sudo dd if=ubuntu.iso of=/dev/sdc bs=2048

Caution: here you are writing directly on a block devices. If you do something wrong... you will ruin your disk and need to reformat it.

find

The find command helps us to find files based on different criteria. Look at this:

$ find . -iname "[a-j]*"
./howcool.sort
./alldata
./mydir/howcool.sort
./mydir/newDir/insideNew
./howcool
  • the first parameter says where should we search (including subdirectories).
  • the -name switch indicates the criteria (here iname means search files with this name and ignore the character cases (z equals Z)).

Another common switch is -type to indicate type we are searching for (f for regular files, d for directories and l for symbolic links):

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ find . -type d -iname "[a-j]*"
./directory
./directory/innder_one

if you want to search for file sizes do as below:

command meaning
-size 100c files which are exactly 100 characters/bytes (you can also use b)
-size +100k files which are more than 100 kilobytes
-size -20M files smaller than 20Megabytes
-size +2G files bigger than 2Gigabytes

So this will find all files ending in tmp with size between 1M and 100M in /var/ directory:

find /var -iname '*tmp' -size +1M -size -100M

you can find all empty files with find . -size 0b or find . -empty

Another useful search criteria is time. These are some of the options:

switch meaning samples
-amin Access Minutes -amin 40 means "files accesses exactly 40min ago" or -amin +40 mins files accessed more than 40min ago and -amin -40 means files accessed less than 40min ago
-cmin Status Change Min -cmin +60 file status changed before last hour
-mmin Modified Minutes -mmin -60 will give us files modified in last hour
-atime access time in days -atime +1 means files access "more than 1 days ago (which means 2 days and more)
-ctime Status Changed in Days
-mtime Modified days
-newer Newer than reference -newer file1 will give you files which are newer than file1

if you add -daystart switch to -mtime or -atime it means that we want to consider days as calendar days, starting at midnight.

Acting on files

We can execute commands or do other actions on files with various switches:

switch meaning
-ls will run ls -dils on each file
-print will print the full name of the files on each line

But the best way to run commands on found files is -exec switch. You can point to the file with '{}' or {} and finish your command with \;.

For example This will remove all empty files in this directory and its subdirectories:

find . -empty -exec rm '{}' \;

or this will rename all htm files to html

find . -name "*.htm" -exec mv '{}' '{}l' \;

since deleting found files is a common task, there is switch for it: -delete

Compression

gzip & gunzip

Straight forward, one gzips files and one ungzips files; In place:

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 20K
-rw-rw-r-- 1 jadi jadi  207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi   29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi   24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi    0 Aug 14 05:08 new_file
-rw-rw-r-- 1 jadi jadi  116 Aug 14 05:08 note_to_self
drwxrwxr-x 3 jadi jadi 4.0K Aug 14 05:20 directory
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 20K
-rw-rw-r-- 1 jadi jadi  171 Aug 14 04:43 tasks.txt.gz
-rw-rw-r-- 1 jadi jadi   29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi   24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi    0 Aug 14 05:08 new_file
-rw-rw-r-- 1 jadi jadi  116 Aug 14 05:08 note_to_self
drwxrwxr-x 3 jadi jadi 4.0K Aug 14 05:20 directory
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ gunzip tasks.txt.gz
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 20K
-rw-rw-r-- 1 jadi jadi  207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi   29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi   24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi    0 Aug 14 05:08 new_file
-rw-rw-r-- 1 jadi jadi  116 Aug 14 05:08 note_to_self
drwxrwxr-x 3 jadi jadi 4.0K Aug 14 05:20 directory
  • gzip preserves time
  • gzip creates the new compressed file with the same name but with .gz ending
  • gzip removes the original files after creating the compressed file (you can keep the input file with -k switch)

bzip2 & bunzip2

The bzip2 is another compressing tool. Works just like the famous gzip but with a different compression algorithm.

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ bzip2 tasks.txt
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls  -ltrh
total 20K
-rw-rw-r-- 1 jadi jadi  172 Aug 14 04:43 tasks.txt.bz2
-rw-rw-r-- 1 jadi jadi   29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi   24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi    0 Aug 14 05:08 new_file
-rw-rw-r-- 1 jadi jadi  116 Aug 14 05:08 note_to_self
drwxrwxr-x 3 jadi jadi 4.0K Aug 14 05:20 directory
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ bunzip2 tasks.txt.bz2
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls
data.txt  directory  info.txt  new_file  note_to_self  tasks.txt

xz & unxz

Another compression / decompression tool just like gzip and bzip2.

jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ xz tasks.txt
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 24K
-rw-rw-r-- 1 jadi jadi  224 Aug 14 04:43 tasks.txt.xz
-rw-rw-r-- 1 jadi jadi   29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi   24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi  116 Aug 14 05:08 note_to_self
drwxrwxr-x 3 jadi jadi 4.0K Aug 14 05:20 directory
-rw-rw-r-- 1 jadi jadi  116 Aug 14 07:51 new_file
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ unxz tasks.txt.xz
jadi@lpicjadi:~/lpic1-practice-iso/100/103.3$ ls -ltrh
total 24K
-rw-rw-r-- 1 jadi jadi  207 Aug 14 04:43 tasks.txt
-rw-rw-r-- 1 jadi jadi   29 Aug 14 04:43 info.txt
-rw-rw-r-- 1 jadi jadi   24 Aug 14 04:44 data.txt
-rw-rw-r-- 1 jadi jadi  116 Aug 14 05:08 note_to_self
drwxrwxr-x 3 jadi jadi 4.0K Aug 14 05:20 directory
-rw-rw-r-- 1 jadi jadi  116 Aug 14 07:51 new_file

Please note that compressing a small text file makes it larger. This is normal in small files because of all the headers and metadata.

In some cases, commands like unxz is just a calls to xz --dcompress

Archiving with tar & cpio

Sometimes we need to create an archive file container of many other files. This operation is different than compressing, its combining files into one and then extracting them again. Archiving is mostly used in backups, moving files to a new location (say via email) and such. This is done with cpio and tar.

tar

TapeARchive or tar is the most common archiving tool. In automatically create an archive file from a directory and all its subdirs.

Common switches are:

switch meanint
-cf myarchive.tar create file named myarchive.tar
-xf myarchive.tar extract a file named myarchive.tar
-z compress the archive with gzip after creating it
-b compress the archive with bzip2 after creating it
-v verbose! print a lot of data about what is happening
-r append new files to the currentyp available archive

If you issue absolute paths, tar removes the starting slash (/) for safety reasons when creating an archive. If you want to override, use -p option.

tar can work with tapes and other storages. Thats why we use -f to tell it that we are working with files.

cpio

Gets a list of files and creates an archive (one file). This file can be used later to extract the original files.

$ ls | cpio -o > allfilesls.cpio
3090354 blocks
  • -o tells cpio to create an output from its input

Please note that cpio does not looks into the folders. So mostly we use it with find:

find . -name "*" | cpio -o > myarchivefind.cpio

To extract the original files:

mkdir extract
mv myarchivefind.cpio extract
cd extract
cpio -id < myarchivefind.cpio
  • -d will create the folders
  • -i is for extract

← 103.2 Process text streams using filters
Chapter List
103.4 Use streams, pipes and redirects →

Category

LPIC1

Tags

Contact