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#] 25Sep2023 search "Linux and how do I revese a string?"

+-----+
https://stackoverflow.com/questions/11461625/reverse-the-order-of-characters-in-a-string
reverse the order of characters in a string
Asked 12 years, 8 months ago
Modified 12 months ago
Viewed 116k times

+--+
Simple:
	var="12345"
	copy=${var}
	
	len=${#copy}
	for((i=$len-1;i>=0;i--)); do rev="$rev${copy:$i:1}"; done
	
	echo "var: $var, rev: $rev"

Output:
	$ bash rev
	var: 12345, rev: 54321

answered Jan 23, 2011 at 6:41
osdyng

+--+
Presume that a variable 'var' has the value '123'
	var="123"
Reverse the string and store in a new variable 'rav':
	rav=$(echo $var | rev)
You'll see the 'rav' has the value of '321' using echo.
	echo $rav

answered Feb 12, 2014 at 22:00
Nick

>> Howell: 
18:22$ echo 'Reverse the string and store in a new variable "rav":'  |  rev
:"var" elbairav wen a ni erots dna gnirts eht esreveR
~

+--+
rev | tail -r (BSD) or rev | tac (GNU) also reverse lines:
	$ rev <<< $'12\n34' | tail -r
	43
	21
	$ rev <<< $'12\n34' | gtac
	43
	21
If LC_CTYPE is C, rev reverses the bytes of multibyte characters:
	$ LC_CTYPE=C rev <<< あの
	��め�
	$ export LC_ALL=C; LC_ALL=en_US.UTF-8 rev <<< あの
	のあ

answered Apr 11, 2013 at 8:56
Lri

+--+
A bash solution improving over @osdyng answer (my edit was not accepted):
	var="12345"     rev=""
	for(( i=0 ; i<${#var} ; i++ )); do rev="${var:i:1}$rev"; done
	echo "var: $var, rev: $rev"

Or an even simpler (bash) loop:
	var=$1   len="${#var}"   i=0   rev=""
	while (( i<len )); do rev="${var:i++:1}$rev"; done
	echo "var: $var, rev: $rev"

A POSIX solution:
	var="12345"     rev=""    i=1
	while  [ "$i" -le "${#var}" ]
	do     rev="$(echo "$var" | awk -v i="$i" '{print(substr($0,i,1))}')$rev"
			: $(( i+=1 ))
	done
	echo "var: $var, rev: $rev"
	Note: This works on multi byte strings. Cut solutions will work only in ASCII (1 byte) strings.

edited Jan 8, 2016 at 3:36
answered Jan 8, 2016 at 1:50
user2350426




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