Advanced Bash-Scripting - 문자열

문자열 길이

• ${#string}
• expr length $string
  
  
  

문자열 바꾸기

vim의 문자열 치환에 익숙하다면 비교적 쉽게 사용할 수 있다.

${string/substring/replacement}

문자열 string에서 첫번째로 일치하는 substring를 찾아서 replacement문자열로 바꾼다.

${string//substring/replacement}

문자열 strng에서 substring과 일치하는 모든 문자열을 찾아서 replacement문자열로 바꾼다.

stringZ=abcABC123ABCabc

echo ${stringZ/abc/xyz}       # xyzABC123ABCabc
                              # Replaces first match of 'abc' with 'xyz'.

echo ${stringZ//abc/xyz}      # xyzABC123ABCxyz
                              # Replaces all matches of 'abc' with # 'xyz'.

echo  ---------------
echo "$stringZ"               # abcABC123ABCabc
echo  ---------------
                              # The string itself is not altered!

# Can the match and replacement strings be parameterized?
match=abc
repl=000
echo ${stringZ/$match/$repl}  # 000ABC123ABCabc
#              ^      ^         ^^^
echo ${stringZ//$match/$repl} # 000ABC123ABC000
# Yes!          ^      ^        ^^^         ^^^

echo

# What happens if no $replacement string is supplied?
echo ${stringZ/abc}           # ABC123ABCabc
echo ${stringZ//abc}          # ABC123ABC
# A simple deletion takes place.

${string/#substring/replacement}

문자열 string의 처음에 일치하는 substring을 replacement 문자열로로 변환한다.

${string/%substring/replacement}

문자열 string의 마지막에 일치하는 substring을 replacement 문자열로로 변환한다.

[출처 : http://www.joinc.co.kr/modules/moniwiki/wiki.php/Site/Bash/AdvancedBashScripting]/Chapter10]

=================================================================================

# 일련변호 만들기1 

echo {a..z}

 

a b c d e f g h i j k l m n o p q r s t u v w x y z

 

echo {0..20}

 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

 

#일련번호 만들기2

seq 1 10

 

# read file.

File=/etc/fstab

{
read line1
read line2
} < $File

echo "First line in $File is : "
echo "$line1"
echo "Second line in $File is : "
echo "$line2"

exit 0

 

# exit status variable

$?

 

#process ID variable

$$

 

# command group

()

 

# block of code

{}

 

# copies "file22.txt" to "file22.backup"

cp file22.{txt,backup}

 

# place for text

ls . | xargs -i -t cp ./{} $1

 

# test

[ ]

 

#test

[[ ]]

 

# array element

[]

 

# range of characters

[]

 

# integer expansion.

[...]

 

#integer expansion

(( ))

 

#redirection

command &> filename : redirects both the stdout and th stderr of command to filename

command >&2 : redirects stdout of command to stderr

[ i ] <> filename : opens file filename for reading and writing. and assigns file descriptor i to it. if filename does not exist, it is created.

<< : redirection used in a hear document.

<<< : redirection used in a hear string.

<,> : ascii comparison.

 

# 문자열 비교하기.

s1=a
s2=a
if [[ "$s1" < "$s2" ]] ; then  # [] 으로 테스트를 하면 에러이다. [[ ]] 으로 테스트를 해야 함.
echo s2 is bigger than s1
else
echo s2 is not bigger than s1
fi

 

# 1에서 100까지 루프 순환하기.

for i in {0..100}

do

echo $i

done

 

#redirection from / to stdin or stdout

echo "whatever" | cat -

 

# note that $variable is actually a simplified form of ${variable}.

 

# number of argument passed.

$#

 

$*

$@ : same as $* , but each parameter is a quoted string. that is, the parameters are passed on intact, without interpretation or expansion.

 

$RANDOM : generate random integer.

 

 

# 실행결과를 변수에 담기.

a=$(ls)

 

# 실행메시지 출력하지 않게 하기.

if cmp a b &> /dev/null  #suppress output.

 

# 파일 테스트.

-e : file exists.

-a : file exists

-f : file is a regular file (not a directory or device file)

-s : file is not zero size

-d : file is a directory

-b : file is a block device

-c : file is a character device

-p : file is a pipe

-h : file is a symbolic link

-L : file is a symbolic link

-S : file is a socket

-t : file is associated with a terminal device

-r : file has read permission

-w : file has write permission

-x : file has execute permission

-g : set-group-id flag set on file or directory

-u : set-user-id flag set on file

-k : sticky bit set

f1 -nt f2 : file f1 is newer than f2

f1 -ot f2 : file f1 is older than f2

f1 -ef f2 : files f1 and f2 are hard links to the same file.

 

# 비교 연산자.(숫자)

-eq : is equal to

if [ "$a" -eq "$b" ]

 

-ne : is not equal to

if [ "$a" -ne "$b" ]

 

-gt : is greater than

if [ "$a" -gt "$b" ]

 

-ge : is greater than or equal to

if [ "$a" -ge "$b" ]

 

-lt : is less than

if [ "$a" -lt "$b" ]

 

-le : is less than or equal to

if [ "$a" -le "$b" ]

 

< : is less than

(( "$a" < "$b" ))

 

<= : is less than or equal to

(( "$a" <= "$b" ))

 

> : is greater than

(( "$a" > "$b" ))

 

 

# 문자열 비교

= : is equal to

if [ "$a" = "$b" ]

 

== : is equal to

if [ "$a" == "$b" ]

 

!= : is not equal to

if [ "$a" != "$b" ]

 

< : is less than

if [[ "$a" < "$b" ]]

if [ "$a" \< "$b" ]

 

> : is greater than. in ASCII alphabetical order.

if [[ "$a" > "$b" ]]

if [ "$a" \> "$b" ]

 

-z : string is null, that is , has zero length

-n : string is not null.

 

# similar to the let command, the (( ... )) construct permits arithmetic expansion and evaluation.

 

# c-style manipulation of variable.

(( a = 23 ))

(( a++))

((++a))

((a--))

((--a))

 

#internal field separator

$IFS

 

$BASH_VERSION

$CDPATH

$DIRSTACK

$EDITOR

$EUID

$FUNCNAME

$FLOBIGNORE

$GROUPS

$HOME

$HOSTNAME

$HOSTTYPE

$LINENO

$MACHTYPE

$OLDPWD

$OSTYPE

$PATH

$PIPESTATUS

$PPID

$PS1 : this is the main prompt.seen at the command-line

$PS2 : the secondary prompt. seen when additional input is expected. is displays as ">"

$PS3 : the tertiary prompt, displayed in a select loop

$PS4 :

$PWD

$REPLY

$SECONDS : the number of seconds the script has been running

$SHLVL : shell level, how deeply bash is nested.

 

# 문자열 조작.

 

#문자열 길이.

${#string}

expr length $string

expr "$string":'.*'

 

# length of matching substring at beginning of string

expr match "$string" "$substring"

expr "$string":'$substring'

stringZ=abcABC123ABCabc 

#       |------| 

#       12345678 

echo `expr match "$stringZ" 'abc[A-Z]*.2'`         # 8 

echo `expr "$stringZ" : 'abc[A-Z]*.2'`             # 8 

 

#index

expr index $string $substring

stringZ=abcABC123ABCabc

#       123456 

echo `expr index "stringZ" C12`             # 6 

 

#substring extractin 

${string:position} 

${string:position:length} 

expr substr $string $position $length 

 

#substring removal 

${string#substring} : deletes shortes match of $substring from front of $string 

${string##substring} : deletes longest match of $substring from front of $string. 

${string%substring} : deletes shortes match of $substring from back of $string 

${string%%substring} : deletes longest match of $substring from back of $string 

 

# variable length / substring removal 

${#var} : string length  

 

# variable expansion / substring replacement 

${var:pos} 

${var:pos:len} 

${var/Pattern/Replacement} 

${var//Pattern/Replacement} : global replacement. all matches of pattern, within var replaced with replacement. 

${var/#Pattern/Replacement} : if prefix of var matches Pattern, then substitute replacement for Pattern 

${var/%Pattern/Replacement} : if suffix of var matches pattern, then substitute replacement for pattern. 

${!varprefix*}, ${!varprefix@} : matches names of all previously declared variables beginning with varprefix. 

 

# loops and branches 

# for 

for arg in [ list ]  ; do

done

 

# while

while [ condition ] ; do

done

 

#until

until [ condition-is-true ]

do

  command(s)...

done

[출처] abs - advanced bash scripting. 정리.|작성자 대운