bash-guide/README.md

İçindekiler

1. Basit Komutlar
   1.1. Dosya Komutlar
   1.2. Text Komutları
   1.3. Dizin Komutları
   1.4. SSH, Sistem Bilgisi & Ağ Komutları
   1.5. İşlem Gösterme Komutları
2. Basic Shell Programming
   2.1. Değişkenler
   2.2 Diziler
   2.3. String Yerleştirme
   2.4. Fonksiyonlar
   2.5. Koşullar(if)
   2.6. Döngüler
3. İpuçları
4. Debugging

1. Basit Komutlar

a. export

Tüm çevre değişkenlerini göstermek için kullanılır. Özel bir çevre değişkeni özelliğini görüntülemek için, echo $VARIABLE_NAME kullanın.

export

Örnek:

$ export
AWS_HOME=/Users/omergulen/.aws
LANG=en_US.UTF-8
LC_CTYPE=en_US.UTF-8
LESS=-R

$ echo $AWS_HOME
/Users/omergulen/.aws

b. whatis

whatis kullanıcı komutları, sistem çağrıları, kütüphane fonksiyonları ve manuel sayfasındaki diğer şeylerin açıklamasını görüntüler.

whatis bir_sey

Örnek:

$ whatis bash
bash (1)             - GNU Bourne-Again SHell

c. whereis

whereis çalıştırabilir dosyaları, kaynak kodlarını ve manuel sayfalarını sistem tarafından otomatik oluşturulan bir veri tabanı ile araştırır.

whereis isim

Örnek:

$ whereis php
/usr/bin/php

d. which

which çalıştırabilir dosyaları belirtilmiş bir PATH (yol) içerisinde arar. Bu komut aranan çalıştırabilirlerin tam yolunu yazdırır.

which program_adi 

Örnek:

$ which php
/c/xampp/php/php

e. clear

Pencere içeriğini temizler.

1.1. Dosya Komutları

cat	chmod	chown	cp	diff	file	find	gunzip	gzcat	gzip	head
lpq	lpr	lprm	ls	more	mv	rm	tail	touch

a. cat

UNIX veya Linux altında, aşağıdaki amaçlar için kullanılır.

• Text dosyalarını ekranda gösterir
• Text dosyalarını kopyalar
• Text dosyalarını birleştirir
• Yeni text dosyaları oluşturur

Örnek:

cat dosya_adi
cat dosya1 dosya2 
cat dosya1 dosya2 > yeni_birlesmis_dosya
cat < dosya1 > dosya2 #dosya 1'i dosya2'ye kopyalar.

b. chmod

chmod komutu "change mode" yani mod değiştir anlamına karşılık gelmektedir ve dosyanın veya dizinin okunabilir, yazılabilir ve çalıştırabilir olmasını değiştirebilir. Daha fazla bilgi için bu linki kontrol edin link.

chmod -secenekler dosya_adi
chmod +x -w calistir_ama_yazama

c. chown

chown komutu "change owner" yani sahibini değiştir anlamına karşılık gelmektedir ve verilen dosya veya dizinin sahibini kullanıcı ve grup olarak değiştirebilir. Basit kullanımı önce kullanıcı:grup adı gelir ve sonrasında dosya veya dizin adı verilir.

chown -secenekler kullanici:grop dosya_adi

d. cp

Dosyaları kopyalar.

cp dosya1 dosya2
cp /root/Desktop/file1.txt /var/www/html/file2.php

dosya1 kaynak yolunu dosya2 ise hedef yolunu belirtir.

e. diff

Dosyaları karşılaştırıp, farklılıklarını gösterir.

diff dosya1 dosya2

f. file

Dosya türünü belirler.

file dosya

Örnek:

$ file index.html
 index.html: HTML document, ASCII text

g. find

Dizinde dosya arar.

find dizin secenek duzen(yapi)

Example:

$ find . -name README.md
$ find /home/ -name '*.png'

h. gunzip

Dosyaları gzip ile çıkartır.

gunzip filename

i. gzcat

Çıkarmadan gzip ile sıkıştırılmış dosyalara bakmamızı sağlar.

gzcat dosya

j. gzip

Dosyaları sıkıştırır.

gzip dosya

k. head

Dosyanın ilk 10 satırını yazdırır.

head dosya

l. lpq

Yazıcı baskı sırasını yazdırır.

lpq

Örnek:

$ lpq
Sıra    Sahip       İş      Dosya(lar)                      Toplam Boyut
active  omergulen   59      deneme                          399360 bytes
1st     omergulen   60      (stdin)                         0 bytes

m. lpr

Dosyayı yazıcıdan yazdırır.

lpr dosya

n. lprm

Yazıcı baskı sırasından bir iş siler.

lprm is_numarasi

o. ls

Dosyaları listelemek için kullanılır. Hiç bir yol veya dizin göstermezseniz bulunduğunuz dizinde çalışır. -l gibi listeleyip daha çok bilgi veren ve -a gibi tüm dosyaları (gizliler dahil) gösteren parametreleri vardır. Daha detaylı bilgi için link.

ls secenek

Örnek:

$ ls -la
rwxr-xr-x   33 omergulen  staff    1122 Mar 27 18:44 .
drwxrwxrwx  60 omergulen  staff    2040 Mar 21 15:06 ..
-rw-r--r--@  1 omergulen  staff   14340 Mar 23 15:05 .DS_Store
-rw-r--r--   1 omergulen  staff     157 Mar 25 18:08 .bumpversion.cfg
-rw-r--r--   1 omergulen  staff    6515 Mar 25 18:08 .config.ini
-rw-r--r--   1 omergulen  staff    5805 Mar 27 18:44 .config.override.ini
drwxr-xr-x  17 omergulen  staff     578 Mar 27 23:36 .git
-rwxr-xr-x   1 omergulen  staff    2702 Mar 25 18:08 .gitignore

p. more

Dosyanın ilk kısmını gösterir (Space ile hareket eder ve q ile çıkılır).

more dosya

q. mv

Dosyayı taşır.

mv dosya1 dosya2

dosya1 kaynak yolunu dosya2 ise hedef yolunu belirtir.

Ayrıca dosyanın ismini değiştirmek için kullanır.

mv eski_isim yeni_isim

r. rm

Dosyaları silmeye yarar. Bunu bir dizin üzerinde kullanmaya çalışmak hataya yol açar. rm: directory: is a directory To remove a directory you have to pass -r which will remove the content of the directory recursively. Optionally you can use -f flag to force the deletion i.e. without any confirmations etc. Dizin silmek için -r kullanmalısınız. Silinmeyen dosyaları zorla silmek için de -f komutu kullanılmaktadır.

rm dosya

s. tail

Outputs the last 10 lines of file. Use -f to output appended data as the file grows.
Dosyanın son 10 satırını yazdırır. -f parametresiyle çıktıyı sona ekler dosya büyüdükçe.

tail dosya

t. touch

Yetki ve zaman etiketini günceller. Böylelikle dosya var olmamışsa yaratır.

touch dosya

Örnek:

$ touch trick.md

1.2. Text Operations

awk	cut	echo	egrep	fgrep	fmt	grep	nl	sed	sort
tr	uniq	wc

a. awk

awk is the most useful command for handling text files. It operates on an entire file line by line. By default it uses whitespace to separate the fields. The most common syntax for awk command is

awk '/search_pattern/ { action_to_take_if_pattern_matches; }' file_to_parse

Lets take following file /etc/passwd. Here's the sample data that this file contains:

root:x:0:0:root:/root:/usr/bin/zsh
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync

So now lets get only username from this file. Where -F specifies that on which base we are going to separate the fields. In our case it's :. { print $1 } means print out the first matching field.

awk -F':' '{ print $1 }' /etc/passwd

After running the above command you will get following output.

root
daemon
bin
sys
sync

For more detail on how to use awk, check following link.

b. cut

Remove sections from each line of files

example.txt

red riding hood went to the park to play

show me columns 2 , 7 , and 9 with a space as a separator

cut -d " " -f2,7,9 example.txt

riding park play

c. echo

Display a line of text

display "Hello World"

echo Hello World

Hello World

display "Hello World" with newlines between words

echo -ne "Hello\nWorld\n"

Hello
World

d. egrep

Print lines matching a pattern - Extended Expression (alias for: 'grep -E')

example.txt

Lorem ipsum
dolor sit amet, 
consetetur
sadipscing elitr,
sed diam nonumy
eirmod tempor
invidunt ut labore
et dolore magna
aliquyam erat, sed
diam voluptua. At
vero eos et
accusam et justo
duo dolores et ea
rebum. Stet clita
kasd gubergren,
no sea takimata
sanctus est Lorem
ipsum dolor sit
amet.

display lines that have either "Lorem" or "dolor" in them.

egrep '(Lorem|dolor)' example.txt
or
grep -E '(Lorem|dolor)' example.txt

Lorem ipsum
dolor sit amet,
et dolore magna
duo dolores et ea
sanctus est Lorem
ipsum dolor sit

e. fgrep

Print lines matching a pattern - FIXED pattern matching (alias for: 'grep -F')

example.txt

Lorem ipsum
dolor sit amet,
consetetur
sadipscing elitr,
sed diam nonumy
eirmod tempor
foo (Lorem|dolor) 
invidunt ut labore
et dolore magna
aliquyam erat, sed
diam voluptua. At
vero eos et
accusam et justo
duo dolores et ea
rebum. Stet clita
kasd gubergren,
no sea takimata
sanctus est Lorem
ipsum dolor sit
amet.

Find the exact string '(Lorem|dolor)' in example.txt

fgrep '(Lorem|dolor)' example.txt
or
grep -F '(Lorem|dolor)' example.txt

foo (Lorem|dolor) 

f. fmt

Simple optimal text formatter

example: example.txt (1 line)

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.

output the lines of example.txt to 20 character width

cat example.txt | fmt -w 20

Lorem ipsum
dolor sit amet,
consetetur
sadipscing elitr,
sed diam nonumy
eirmod tempor
invidunt ut labore
et dolore magna
aliquyam erat, sed
diam voluptua. At
vero eos et
accusam et justo
duo dolores et ea
rebum. Stet clita
kasd gubergren,
no sea takimata
sanctus est Lorem
ipsum dolor sit
amet.

g. grep

Looks for text inside files. You can use grep to search for lines of text that match one or many regular expressions, and outputs only the matching lines.

grep pattern filename

Example:

$ grep admin /etc/passwd
_kadmin_admin:*:218:-2:Kerberos Admin Service:/var/empty:/usr/bin/false
_kadmin_changepw:*:219:-2:Kerberos Change Password Service:/var/empty:/usr/bin/false
_krb_kadmin:*:231:-2:Open Directory Kerberos Admin Service:/var/empty:/usr/bin/false

You can also force grep to ignore word case by using -i option. -r can be used to search all files under the specified directory, for example:

$ grep -r admin /etc/

And -w to search for words only. For more detail on grep, check following link.

h. nl

Number lines of files

example.txt

Lorem ipsum
dolor sit amet,
consetetur
sadipscing elitr,
sed diam nonumy
eirmod tempor
invidunt ut labore
et dolore magna
aliquyam erat, sed
diam voluptua. At
vero eos et
accusam et justo
duo dolores et ea
rebum. Stet clita
kasd gubergren,
no sea takimata
sanctus est Lorem
ipsum dolor sit
amet.

show example.txt with line numbers

nl -s". " example.txt 

     1. Lorem ipsum
     2. dolor sit amet,
     3. consetetur
     4. sadipscing elitr,
     5. sed diam nonumy
     6. eirmod tempor
     7. invidunt ut labore
     8. et dolore magna
     9. aliquyam erat, sed
    10. diam voluptua. At
    11. vero eos et
    12. accusam et justo
    13. duo dolores et ea
    14. rebum. Stet clita
    15. kasd gubergren,
    16. no sea takimata
    17. sanctus est Lorem
    18. ipsum dolor sit
    19. amet.

i. sed

Stream editor for filtering and transforming text

example.txt

Hello This is a Test 1 2 3 4

replace all spaces with hyphens

sed 's/ /-/g' example.txt

Hello-This-is-a-Test-1-2-3-4

replace all digits with "d"

sed 's/[0-9]/d/g' example.txt

Hello This is a Test d d d d

j. sort

Sort lines of text files

example.txt

f
b
c
g
a
e
d

sort example.txt

sort example.txt

a
b
c
d
e
f
g

randomize a sorted example.txt

sort example.txt | sort -R

b
f
a
c
d
g
e

k. tr

Translate or delete characters

example.txt

Hello World Foo Bar Baz!

take all lower case letters and make them upper case

cat example.txt | tr 'a-z' 'A-Z' 

HELLO WORLD FOO BAR BAZ!

take all spaces and make them into newlines

cat example.txt | tr ' ' '\n'

Hello
World
Foo
Bar
Baz!

l. uniq

Report or omit repeated lines

example.txt

a
a
b
a
b
c
d
c

show only unique lines of example.txt (first you need to sort it, otherwise it won't see the overlap)

sort example.txt | uniq

a
b
c
d

show the unique items for each line, and tell me how many instances it found

sort example.txt | uniq -c

    3 a
    2 b
    2 c
    1 d

m. wc

Tells you how many lines, words and characters there are in a file.

wc filename

Example:

$ wc demo.txt
7459   15915  398400 demo.txt

Where 7459 is lines, 15915 is words and 398400 is characters.

1.3. Directory Operations

cd

mkdir

pwd

a. cd

Moves you from one directory to other. Running this

$ cd

moves you to home directory. This command accepts an optional dirname, which moves you to that directory.

cd dirname

b. mkdir

Makes a new directory.

mkdir dirname

c. pwd

Tells you which directory you currently are in.

pwd

1.4. SSH, System Info & Network Operations

bg	cal	date	df	dig	du	fg	finger	last	man
passwd	ping	ps	quota	scp	ssh	top	uname	uptime	w
wget	whoami	whois

a. bg

Lists stopped or background jobs; resume a stopped job in the background.

b. cal

Shows the month's calendar.

c. date

Shows the current date and time.

d. df

Shows disk usage.

e. dig

Gets DNS information for domain.

dig domain

f. du

Shows the disk usage of files or directories. For more information on this command check this link

du [option] [filename|directory]

Options:

• -h (human readable) Displays output it in kilobytes (K), megabytes (M) and gigabytes (G).
• -s (supress or summarize) Outputs total disk space of a directory and supresses reports for subdirectories.

Example:

du -sh pictures
1.4M pictures

g. fg

Brings the most recent job in the foreground.

h. finger

Displays information about user.

finger username

i. last

Lists your last logins of specified user.

last yourUsername

j. man

Shows the manual for specified command.

man command

k. passwd

Allows the current logged user to change his password.

l. ping

Pings host and outputs results.

ping host

m. ps

Lists your processes.

ps -u yourusername

n. quota

Shows what your disk quota is.

quota -v

o. scp

Transfer files between a local host and a remote host or between two remote hosts.

copy from local host to remote host

scp source_file user@host:directory/target_file

copy from remote host to local host

scp user@host:directory/source_file target_file
scp -r user@host:directory/source_folder farget_folder

This command also accepts an option -P that can be used to connect to specific port.

scp -P port user@host:directory/source_file target_file

p. ssh

ssh (SSH client) is a program for logging into and executing commands on a remote machine.

ssh user@host

This command also accepts an option -p that can be used to connect to specific port.

ssh -p port user@host

q. top

Displays your currently active processes.

r. uname

Shows kernel information.

uname -a

s. uptime

Shows current uptime.

t. w

Displays who is online.

u. wget

Downloads file.

wget file

v. whoami

Return current logged in username.

w. whois

Gets whois information for domain.

whois domain

1.5. Process Monitoring Operations

kill

killall

&

nohup

a. kill

Kills (ends) the processes with the ID you gave.

kill PID

b. killall

Kill all processes with the name.

killall processname

c. &

The & symbol instructs the command to run as a background process in a subshell.

command &

d. nohup

nohup stands for "No Hang Up". This allows to run command/process or shell script that can continue running in the background after you log out from a shell.

nohup command

Combine it with & to create background processes

nohup command &

2. Basic Shell Programming

The first line that you will write in bash script files is called shebang. This line in any script determines the script's ability to be executed like a standalone executable without typing sh, bash, python, php etc beforehand in the terminal.

#!/bin/bash

2.1. Variables

Creating variables in bash is similar to other languages. There are no data types. A variable in bash can contain a number, a character, a string of characters, etc. You have no need to declare a variable, just assigning a value to its reference will create it.

Example:

str="hello world"

The above line creates a variable str and assigns "hello world" to it. The value of variable is retrieved by putting the $ in the beginning of variable name.

Example:

echo $str   # hello world

2.2. Array

Like other languages bash has also arrays. An array is variable containing multiple values. There's no maximum limit on the size of array. Array in bash are zero based. The first element is indexed with element 0. There are several ways for creating arrays in bash. Which are given below.

Examples:

array[0] = val
array[1] = val
array[2] = val
array=([2]=val [0]=val [1]=val)
array=(val val val)

To display a value at specific index use following syntax:

${array[i]}     # where i is the index

If no index is supplied, array element 0 is assumed. To find out how many values there are in the array use the following syntax:

${#array[@]}

Bash has also support for the ternary conditions. Check some examples below.

${varname:-word}    # if varname exists and isn't null, return its value; otherwise return word
${varname:=word}    # if varname exists and isn't null, return its value; otherwise set it word and then return its value
${varname:+word}    # if varname exists and isn't null, return word; otherwise return null
${varname:offset:length}    # performs substring expansion. It returns the substring of $varname starting at offset and up to length characters

2.3 String Substitution

Check some of the syntax on how to manipulate strings

${variable#pattern}         # if the pattern matches the beginning of the variable's value, delete the shortest part that matches and return the rest
${variable##pattern}        # if the pattern matches the beginning of the variable's value, delete the longest part that matches and return the rest
${variable%pattern}         # if the pattern matches the end of the variable's value, delete the shortest part that matches and return the rest
${variable%%pattern}        # if the pattern matches the end of the variable's value, delete the longest part that matches and return the rest
${variable/pattern/string}  # the longest match to pattern in variable is replaced by string. Only the first match is replaced
${variable//pattern/string} # the longest match to pattern in variable is replaced by string. All matches are replaced
${#varname}     # returns the length of the value of the variable as a character string

2.4. Functions

As in almost any programming language, you can use functions to group pieces of code in a more logical way or practice the divine art of recursion. Declaring a function is just a matter of writing function my_func { my_code }. Calling a function is just like calling another program, you just write its name.

functname() {
    shell commands
}

Example:

#!/bin/bash
function hello {
   echo world!
}
hello

function say {
    echo $1
}
say "hello world!"

When you run the above example the hello function will output "world!". The above two functions hello and say are identical. The main difference is function say. This function, prints the first argument it receives. Arguments, within functions, are treated in the same manner as arguments given to the script.

2.5. Conditionals

The conditional statement in bash is similar to other programming languages. Conditions have many form like the most basic form is if expression then statement where statement is only executed if expression is true.

if [expression]; then
    will execute only if expression is true
else
    will execute if expression is false
fi

Sometime if conditions becoming confusing so you can write the same condition using the case statements.

case expression in
    pattern1 )
        statements ;;
    pattern2 )
        statements ;;
    ...
esac

Expression Examples:

statement1 && statement2  # both statements are true
statement1 || statement2  # at least one of the statements is true

str1=str2       # str1 matches str2
str1!=str2      # str1 does not match str2
str1<str2       # str1 is less than str2
str1>str2       # str1 is greater than str2
-n str1         # str1 is not null (has length greater than 0)
-z str1         # str1 is null (has length 0)

-a file         # file exists
-d file         # file exists and is a directory
-e file         # file exists; same -a
-f file         # file exists and is a regular file (i.e., not a directory or other special type of file)
-r file         # you have read permission
-s file         # file exists and is not empty
-w file         # your have write permission
-x file         # you have execute permission on file, or directory search permission if it is a directory
-N file         # file was modified since it was last read
-O file         # you own file
-G file         # file's group ID matches yours (or one of yours, if you are in multiple groups)

file1 -nt file2     # file1 is newer than file2
file1 -ot file2     # file1 is older than file2

-lt     # less than
-le     # less than or equal
-eq     # equal
-ge     # greater than or equal
-gt     # greater than
-ne     # not equal

2.6. Loops

There are three types of loops in bash. for, while and until.

Different for Syntax:

for x := 1 to 10 do
begin
  statements
end

for name [in list]
do
  statements that can use $name
done

for (( initialisation ; ending condition ; update ))
do
  statements...
done

while Syntax:

while condition; do
  statements
done

until Syntax:

until condition; do
  statements
done

3. Tricks

Set an alias

Open bash_profile by running following command nano ~/.bash_profile

alias dockerlogin='ssh www-data@adnan.local -p2222' # add your alias in .bash_profile

To quickly go to a specific directory

nano ~/.bashrc

export hotellogs="/workspace/hotel-api/storage/logs"

source ~/.bashrc
cd $hotellogs

Exit traps

Make your bash scripts more robust by reliably performing cleanup.

function finish {
  # your cleanup here. e.g. kill any forked processes
  jobs -p | xargs kill
}
trap finish EXIT

Saving your environment variables

When you do export FOO = BAR, your variable is only exported in this current shell and all its children, to persist in the future you can simply append in your ~/.bash_profile file the command to export your variable

echo export FOO=BAR >> ~/.bash_profile

Accessing your scripts

You can easily access your scripts by creating a bin folder in your home with mkdir ~/bin, now all the scripts you put in this folder you can access in any directory.

If you can not access, try append the code below in your ~/.bash_profile file and after do source ~/.bash_profile.

    # set PATH so it includes user's private bin if it exists
    if [ -d "$HOME/bin" ] ; then
        PATH="$HOME/bin:$PATH"
    fi

4. Debugging

You can easily debug the bash script by passing different options to bash command. For example -n will not run commands and check for syntax errors only. -v echo commands before running them. -x echo commands after command-line processing.

bash -n scriptname
bash -v scriptname
bash -x scriptname

Contribution

• Report issues How to
• Open pull request with improvements How to
• Spread the word

License