command

;　$pwd;ls Execute the right command regardless of whether the left command causes an error or succeeds.

&&　 $ls prog/ruby && pwd Execute the second command only when the first command completes successfully

||　$cat temp||echo "file not found"

The second command is executed only when the first command does not complete successfully.

() $(date;pwd;ls)>kekka.log Execute commands together

"" (Single quotation mark)

$echo ＄DATE ＞ August 31 $echo '＄DATE' ＞＄DATE It is output as a character string.

""(Double quotation)

$echo ＄DATE ＞ August 31 $ echo "Today's date is $ DATE"

Today's date is August 31st. ''Same as. The variable part of $ is output as a variable.

`` (Back quote)

$ echo "The current directory is'pwd'."

The current directory is / home / lpic.

$ echo "The current directory is $ (pwd)'."

The current directory is / home / lpic.

The command result can be output. It is recommended because it is easier to understand how to write below.

less

Key operation	Explanation
Space bar	Scroll down one screen
b key	Scroll up one screen
/	Downward search
?	Upward search

| (Pipe)

ls | wc -l Pass the execution result of the ls command to the standard input of wc.

dmesg|less Pass kernel messages to less standard input.

> (Redirect)

$ls -l > filelist Put the display result in the filelist.

$ls -l >> filelist Added display result to the end of filelist.

< $grep "lpic" <target.txt>result.txt Standard input

$cat > sample.txt <<EOF Output until EOF is input.

2> $find / -name "*.tmp" 2> error.log Save only error output to a file.

cat cat file1 file2 > newfile Application: Write file1 file2 to newfile continuously

option	Explanation
-n	Display with line numbers

nl Display text files with line numbers.

tail Display 10 lines from the last line.

option	Explanation
-n number of lines	Display only the specified number of lines
-f	Real-time display. Update when added during display.(ctrl+End with c)

tr $cat /etc/hosts | tr 'a-z' 'A-Z' Convert all lowercase letters in the file to uppercase and cat

split $split -100 sample.txt s_sample.

sample.txt s_sample.aa s_sample.ab s_sample.ac

Separate sample.txt into other files every 100 lines. (File names end with aa, ab, ac ...)

hash

command	Explanation
md5sum	Output hash value by MD5
sha1sum
sha256sum
sha512sum

$sha1sum sample.txt Show SHA1 hash value of sample.txt file

grep $grep -i ab sample.txt

$grep -v '^#' /etc/httpd/conf/httpd.conf Displayed by omitting the line with # at the beginning (comment out). (^: Regular expression for the first character)

option	Explanation
-i	Case insensitive search
-v	Show lines where patterns do not match

Input mode

command	Explanation
i	Enter text before the cursor
a	Enter text after the cursor
I	Move the cursor to the first character at the beginning of a line and enter text just before it
A	Move the cursor to the end of the line and enter the text immediately after
o	Insert a blank line below the current line and enter text on that line
O	Insert a blank line above the current line and enter text on that line

Command mode

command	Explanation
h	Move one character to the left
l	Move one character to the right
k	Move up one line
j	Move down one line
o	Move to the beginning of the line
$	Move to the end of the line
H	Move to the beginning of the line at the top of the screen
L	Move to the beginning of the line at the bottom of the screen
gg	Move to the first line of the file
G	Move to the last line of the file
nG	Move to line n of the file
:n	Move to line n of the file

Move 5 characters to the left in 5h

command	Explanation
:q	Exit without saving to file
:q!	Exit without saving what you are editing
:wq	Save the content being edited and exit
:w	Overwrite and save the file with the content being edited
:e!	Restore to the last saved content
:!command	Execute shell command without exiting vi
:r!command	Insert the execution result of the shell command

:! You can execute the ls command with ls running vi.

vi edit command

command	Explanation
dd	Delete current line
dw	Delete from one cursor to the next word
yy	Copy the current line to the buffer
:w	Overwrite and save the file with the content being edited
p	Paste the contents of the buffer below the current line
P	Paste the contents of the buffer above the current line
x	Delete the character at the cursor position(delete)
X	Delete the character before the cursor position(backspace)

Delete 5 lines from the cursor position with 5dd.

vi search command

command	Explanation
/	Search backward from the cursor position
?	Search backward from the cursor position
n	Search for
N	Search for(Reverse direction)
:noh	Unhighlight candidates
:%s/A/B/	Replace the first found string A with the string B
:%s/A/B/g	Replace all strings A with string B

command	Explanation
:set nu	Display line numbers
:set nonu	Hide line number h
:set ts=Tab width	Tab widthを数値で指定する

File management

gzip

command	Explanation
-d	Extract the compressed file
-c	Output to standard output
-r	Compress all files in the directory

$gzip datafile Compress file

$gzip -r sampled Compress all files in the sampled directory individually

$gzip -c datafile >datafile.gz Compressed leaving the folder before compression

$bzip2 datafile bzip takes longer than gzip but has higher compression efficiency. (Add option -d for decompression)

$xz datafile xz takes longer than bzip but has higher compression efficiency. (Add option -d for decompression)

zcat,bzcat,xzcat $zcat sample.gz Check the compressed text file without decompressing it.

tar You can combine files and directories into a single archive file and unpack it. Same as gzip compression with z option.

command	Explanation
-c	Create an archive
-x	Extract files from archive
-t	Check the contents of the archive
-f file name	Specify the archive file name
-z	gzip compression/Deployment
-j	bzip2 compression/Deployment
-J	xz compression/Deployment
-v	Display detailed information
-u	Add only newer files with the same name in the archive
-r	Add files to the archive
-N	Only targets data newer than the specified date
-M	Split into multiple devices
-delete	Delete files from the archive

tar cvf /dev/st0 /home Create / home archive file in / dev / st0

tar xvzf software.tar.gz Extract the archive file to the current directory.

tar tf /dev/sdb1 View the contents of the archive located in / dev / sb1.

tar xvf /dev/sdb1 var/log/secure /var

cpio $ls | cpio -o >/tmp/backup Back up the current directory as a / tmp / backup file.

dd $dd if=/dev/sdb of=/dev/sdc Output the contents of the disk connected to / dev / sdb to / dev / sdb as it is.

The dd command can handle the contents of devices such as hard disks and CD-ROMs as they are. The cp command just copies the file.

command	Explanation
-if	Specify the input file
-of	Specify the output file

chmod

option	Explanation
-R	Change the permissions of all files under the specified directory

Target	Explanation
u	owner
g	group
o	Other users
a	All users

operation	Explanation
+	Add permissions
-	Remove permissions
=	Specify permissions

Type of permission	Explanation
r	Read permission
w	Write permission
x	Execution permission
s	SUID or SGID
t	Sticky bit

$chmod go+w samplefile Give write permission to groups and other users

$chmod o-rw samplefile Eliminate write execution authority from other users

$chmod 644 samplefile Changed to 644

SUID,SGID Can be executed with the privileges of the owner of the SUID file

chmod u+s samplefile

SGID group access rights apply.

Sticky bit

Even if you have write permission, you cannot delete files owned by users other than yourself.

chmod o+t sampledir

umask The default access right is set.

$umask 0002

The default is 777 for directories and 666 for files minus umask.

d→775 file→664

chown

option	Explanation
-R	Change the owner of the specified directory and all files in it

Hard link

Refer to the same entity in each file. $ln file.original file.link_hard

Symbolic link

Indicates the location under the link. (Shortcut) $ln -s file.original file.link_hard

ls -l Check the created link.

Add d to the copy of the symbolic link.

cp -d file.link_sym file.link3

If not added, the link source file will be copied. cp file.link_sym file.link2

top Process monitoring End with Q

Run background job

updatedb & You can execute the process in the background by adding &.

jobs You can check the running jobs with the jobs command.

I want you to keep doing it when you leave your seat for a long time. If you want it to run even if you log out. Add nohub. $nohup updatedb &

If you want to run the currently running job in the background. Pause with ctrl + z → bg 1 (1 is the job number, jobs) If you want to change the background to the foreground, fg

free Memory availability

option	Explanation
-m	Display in MB
-s seconds	Continue to display at specified intervals

uptime Average load etc.

uname OS check

uname -a Detail View

watch watch -n 10 uptime Run uptime every 10 seconds.

nice Specify the priority when executing the command. $nice -n -10 updatedb

Device management File management

find $find /root -name "*.txt" Search by file name

Search formula	Explanation
-name file name	Search by file name
-atime date and time	Search by last access time
-mtime date and time	Search by last update time
-perm access	Search by access right
-size size	Search by file size
-type File type	Search by file type f:File l:Symbolic d:directory
-user username	Search by file owner
-print	Show matched files
-exec command ｜｜ ;	Execute command for matching files
-ok command ｜｜ ¥;	Execute command for matching files(With confirmation)

$find /data -type f -mtime -1 Search for files updated within the last day

$find /usr/bin -type f -perm -u+s Search for files with SUID under the / usr / bin directory.

$find /tmp -user student Find the file directory whose owner is student.

$find -atime +30 -exec rm {}¥; Find and delete files that have not been accessed for more than 30 days.

Shells and shell scripts

alias

$alias ls='ls -l' You can give the command an alias. $alias lsless='ls -l|less'

$unalias lsless Release the set alias

function

$function lslink(){ls -l|grep '^l';} The lslink function that displays only symbolic links (starting with l)

$function lslink(){ls -l ＄1 | grep '^1';} Argument with $ 1. You can put a directory etc. in the argument.

$declare -f lslink Show only defined functions.

unset lslink Removed lslink function.

bash config file

File	Explanation
/etc/profile	Executed at login and referenced by all users
/etc/bash.basic	Executed when bash is started and referenced by all users
/etc/bashrc	~/.Referenced from bashrc. Referenced from the time bash is started.
~/.bash_profile	Executed at login
~/.bash_login	~/.bash_If there is no profile, it will be executed at login
~/.profile	~/.bash_profile too~/.bash_If you don't have login, run at login
~/.bashrc	Executed when bash starts
~/.bash_logout	Runs when logging out

Shell script

Execute (requires read permission) $bash lsld

$source lsld

$. lsld

(Execution authority required) chmod a+x lsld $./lsls It is executed with the file name as it is.

Variable name	Explanation
$0	Shell script file name(full path)
$1	1st argument
$2	The second argument. Below $ 3 $ 4 $ 5
$#	Number of arguments.
$@	All arguments(Space delimited)
$*	All arguments(The delimiter is the one specified by the environment variable IFS)

Return value of execution result

Normal termination → 0 Abnormal termination → other than 0

＄echo $? 2

The return value is assigned to $ ?.

File check

test command

Conditional expression	Execution result
	File format test
-f file	(Excluding directories etc.)True if there is a file
-d directory	True if there is a directory
-r file	True if the file exists and is readable
-w file	True if the file exists and is writable
-x file	True if the file exists and is executable
-s file	True if there are files larger than 0
-L file	True if there is a file that is a symbolic link
	File property testing
-e file	True if there is a file
File 1-nt file 2	True if file 1 has a newer modification time than file 2
File 1-ot file 2	True if file 1 is older than file 2
	Numerical test
Number 1-eq number 2	True if number 1 and number 2 are equal
Number 1-ge number 2	True if number 1 is greater than or equal to number 2.
Number 1-gt number 2	True if number 1 is greater than number 2
Number 1-le number 2	True if number 1 is less than or equal to number 2
Number 1-lt number 2	True if number 1 is less than or equal to number 2
Number 1-ne number 2	True if number 1 and number 2 are not equal
	String test
-n string	True if the length of the string is greater than 0
-z string	True if the length of the string is 0
String 1=String 2	True if the two strings are equal
String 1!=String 2	True if the two strings are not equal
	Logical join of tests
!conditions	conditionsが偽であれば真
Condition 1-a Condition 2	True if both conditional expressions are true(and)
Condition 1-o Condition 2	True if any conditional expression is true(or)

Conditional branch

if conditional expression then Execution statement 1 else Execution statement 2 fi

Case case $1 in 1)echo "January";; 2)echo "February";; esac

read You can hear the name from the standard input. echo -n "Who are you?:" read username ← Ask the user here echo "Hello, $ username!" ← Used here

First line of shell script ＃!/bin/bash

Administrative tasks

File for which user account is set /etc/passwd

group /etc/group

useradd useradd -c "Linux User" -d /home/linux -s /bin/bash linuxuser

option	Execution result
-c comment	Specify comment field
-d directory	Specify home directory
-s path	Specify default shell

Job scheduling

cron

crontab It is located under the / var / spool / cron directory.

option	Execution result
-e	Edit crontab(Do not open directly with vi etc.)
-l	Content display
-r	File deletion
-i	Confirm when deleting
-u username	Edit the crontab file with a username(root user only)

Format Minute, hour, day, month, day of the week command

field	Execution result
Day of the week	0-Integer up to 7(0,7:Sunday to 6th Saturday)

15 23 * * * /usr/local/bin/backup (Starts every day at 23:15)

0 9,12 * * 1 /usr/local/bin/syscheck (Starts at 09:00 and 12:00 on Mondays)

0 */2 * * * /usr/local/bin/syscheck (Start every 2 hours)

at One-time scheduling $at 5:00 tomorrow at>/usr/local/sbin/backup at> ^ D ← Enter ctrl + D key to finish.

systemd It can be activated after a certain period of time from some event.

Email

mail [-s subject] [destination email address or user name]

mail -s samplemail student Hello! Student! ← Body . EOT

mail Check received email

Network basics

ping

option	Execution result
-c times	Send packets a specified number of times
-i interval	Specified interval(Seconds)Send every pocket

traceroute Displays the route through which the packet travels to the specified host.

hostname Display the current host name.

If you specify a host name, change the host name.

netstat Display various information about the network. Checking open ports, etc.

nc Cat command on the network

$nc -l -p 12345 -o listen.log It listens on port 12345 and outputs the received data to the listen.log file.

$nc centos7.example.com 12345<data.txt Output the contents of the data.txt file to the 12345 port of the host.

ifconfig Confirmation of ip address.

DNS configuration file

/etc/resolv.conf

/etc/nsswitch.conf Select the order of prioritizing hosts or DNS server.

host Know the host ip. Know the host of ip.

Security

nmap

$nmap www.example.net You can check the open port number and service name (ssh, http).

How to check which files have SUID set.

Check regularly. ＃find / -perm -u+s -ls

Stop login for general users

＃touch /etc/nologin By creating a nologin file, logins other than the root are prohibited.

scp scp copy source file name [user name @] copy destination host: [copy destination file name]

scp /etc/hosts sv3.example.jp:/tmp Copy / etx / hosts on the local host to / tmp on the remote host sv3.example.jp.

scp [user name @] copy source host: copy source file name copy destination file name

$scp sv3.example.jp:/etc/hosts . Copy / etc / hosts of remote host sv3.example.jp to the current directory.

$scp data.txt [email protected]: Copy the data.txt file of the local host to the home directory of the fred user of the remote host sv3.example.jp

Linux Summary