I have read many tutorials on the internet about the usage of the 'tr' command.
However, I am not able to understand how to encrypt an email address with a shell script shift the characters using rot13. Can any one give a link or an example?
Not sure exactly how you want to use this, but here's a basic example to get you started:
echo 'fooman#example.com' | tr 'A-Za-z' 'N-ZA-Mn-za-m'
To make it easier, you can alias the tr command in your .bashrc file thusly:
alias rot13="tr 'A-Za-z' 'N-ZA-Mn-za-m'"
Now you can just call:
echo 'fooman#example.com' | rot13
A perfect task for tr, indeed. This should do what you want:
tr 'A-Za-z' 'N-ZA-Mn-za-m'
Each character in the first set will be replaced with the corresponding character in the second set. E.g. A replaced with N, B replaced with O, etc.. And then the same for the lower case letters. All other characters will be passed through unchanged.
Note the lack of [ and ] where you normally might expect them. This is because tr treats square brackets literally, not as range expressions. So, for example, tr -d '[A-Z]' will delete capital letters and square brackets. If you wanted to keep your brackets, use tr -d 'A-Z':
$ echo "foo BAR [baz]" | tr -d '[A-Z]'
foo baz
$ echo "foo BAR [baz]" | tr -d 'A-Z'
foo [baz]
Same for character classes. E.g. tr -d '[[:lower:]]' is probably an error, and should be tr -d '[:lower:]'.
However, in lucky situations like this one, you can get away with including the brackets anyway! For example, tr "[a-z]" "[A-Z]" accidentally works because the square brackets in the first set are replaced by identical square brackets from the second set, but really this is a bad habit to get into. Use tr "a-z" "A-Z" instead.
Ruby(1.9+)
$ ruby -ne 'print $_.tr( "A-Za-z", "N-ZA-Mn-za-m") ' file
Python
$ echo "test" | python -c 'import sys; print sys.stdin.read().encode("rot13")'
to simultaneously do ROT13 (for letters) and ROT5 (for numbers):
tr 'A-Za-z0-9' 'N-ZA-Mn-za-m5-90-4'
usage:
echo test | tr 'A-Za-z0-9' 'N-ZA-Mn-za-m5-90-4'
alias definition for your ~/.bashrc in case you need it more often:
alias rot="tr 'A-Za-z0-9' 'N-ZA-Mn-za-m5-90-4'"
(accurately rot135 or rot18)
# Reciprocal Transformation(s)
# rot13
tr 'A-Za-z' 'N-ZA-Mn-za-m' <<< 'user#domain.com'
# rot13.5 (rot18)
tr 'A-Za-z0-9' 'N-ZA-Mn-za-m5-90-4' <<< 'user123#domain.com'
# rot47
tr '\!-~' 'P-~\!-O' <<< 'user123#domain.com'
# rot13 -- SED anyone
echo 'user#domain.com' | sed y/NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz/
Shell Script
#!/bin/bash
# Purpose: Rotate 13 characters (a reciprocal transformation)
# ./rot13.sh 'A String to look Ciphered'
tr 'A-Za-z' 'N-ZA-Mn-za-m' <<< "$1"
exit $?
You can execute it inside a shell script
#!/bin/bash
echo 'rot13#rot.com' | tr 'A-Za-z' 'N-ZA-Mn-za-m'
echo 'rot13#rot.com' | rot13
Make the file executable by running:
sudo chmod +x file_name
To ouput the answer run:
./file_name
example:
./try.sh
Related
x=`unzip -l "$i" | grep /config.xml | tail -1 | sed -e "s/.*:[0-9][0-9] *//"`
content=`unzip -c "$i" "$x" | DO MORE STUFF HERE
I am having a problem with the above command whenever x outputs a string with square brackets. For example, let's say that after running the x line, $x = "Refresher [Autosaved]/xml/config.xml". If I pass $x to the content line, I get an error that caution: filename not matched: Refresher [Autosaved]/xml/config.xml. I have tried updating the sed command to escape the brackets with s/\[\([^]]*\)\]/\\\[\1\\\]/g and the values echo out fine, but when I save it to x, the \[ and \] turns into just [ and ] and I am back to square one.
How can I run the content command if my x value has square brackets?
Save yourself a ton of trouble using modern $(...) instead of legacy `...`. The former does not require additional escaping:
$ x=$(echo 'Foo [Bar].baz' | sed "s/\[\([^]]*\)\]/\\\[\1\\\]/g")
$ printf '%s\n' "$x"
Foo \[Bar\].baz
$ x=`echo 'Foo [Bar].baz' | sed "s/\[\([^]]*\)\]/\\\[\1\\\]/g"`
$ printf '%s\n' "$x"
Foo [Bar].baz
I used many times [``] to capture output of command to a variable. but with following code i am not getting right output.
#!/bin/bash
export XLINE='($ZWP_SCRIP_NAME),$ZWP_LT_RSI_TRIGGER)R),$ZWP_RTIMER'
echo 'Original XLINE'
echo $XLINE
echo '------------------'
echo 'Extract all word with $ZWP'
#works fine
echo $XLINE | sed -e 's/\$/\n/g' | sed -e 's/.*\(ZWP[_A-Z]*\).*/\1/g' | grep ZWP
echo '------------------'
echo 'Assign all word with $ZWP to XVAR'
#XVAR doesn't get all the values
export XVAR=`echo $XLINE | sed -e 's/\$/\n/g' | sed -e 's/.*\(ZWP[_A-Z]*\).*/\1/g' | grep ZWP` #fails
echo "$XVAR"
and i get:
Original XLINE
($ZWP_SCRIP_NAME),$ZWP_LT_RSI_TRIGGER)R),$ZWP_RTIMER
------------------
Extract all word with $ZWP
ZWP_SCRIP_NAME
ZWP_LT_RSI_TRIGGER
ZWP_RTIMER
------------------
Assign all word with $ZWP to XVAR
ZWP_RTIMER
why XVAR doesn't get all the values?
however if i use $() to capture the out instead of ``, it works fine. but why `` is not working?
Having GNU grep you can use this command:
XVAR=$(grep -oP '\$\KZWP[A-Z_]+' <<< "$XLINE")
If you pass -P grep is using Perl compatible regular expressions. The key here is the \K escape sequence. Basically the regex matches $ZWP followed by one or more uppercase characters or underscores. The \K after the $ removes the $ itself from the match, while its presence is still required to match the whole pattern. Call it poor man's lookbehind if you want, I like it! :)
Btw, grep -o outputs every match on a single line instead of just printing the lines which match the pattern.
If you don't have GNU grep or you care about portability you can use awk, like this:
XVAR=$(awk -F'$' '{sub(/[^A-Z_].*/, "", $2); print $2}' RS=',' <<< "$XLINE")
First, the smallest change that makes your code "work":
echo "$XLINE" | tr '$' '\n' | sed -e 's/.*\(ZWP[_A-Z]*\).*/\1/g' | grep ZWP_
The use of tr replaces a sed expression that didn't actually do what you thought it did -- try looking at its output to see.
One sane alternative would be to rely on GNU grep's -o option. If you can't do that...
zwpvars=( ) # create a shell array
zwp_assignment_re='[$](ZWP_[[:alnum:]_]+)(.*)' # ...and a regex
content="$XLINE"
while [[ $content =~ $zwp_assignment_re ]]; do
zwpvars+=( "${BASH_REMATCH[1]}" ) # found a reference
content=${BASH_REMATCH[2]} # stuff the remaining content aside
done
printf 'Found variable: %s\n' "${zwpvars[#]}"
I am trying to only change the first letter of a string to lowercase using a Shell script. Ideally a simple way to go from CamelCase to lowerCamelCase.
GOAL:
$DIR="SomeString"
# missing step
$echo $DIR
someString
I have found some great resources for doing this to the entire string but not just altering the first letter and leaving the remaining string untouched.
If your shell is recent enough, you can use the following parameter expansion:
DIR="SomeString" # Note the missing dollar sign.
echo ${DIR,}
Alternative solution (will work on old bash too)
DIR="SomeString"
echo $(echo ${DIR:0:1} | tr "[A-Z]" "[a-z]")${DIR:1}
prints
someString
for assing to variable
DIR2="$(echo ${DIR:0:1} | tr "[A-Z]" "[a-z]")${DIR:1}"
echo $DIR2
prints
someString
alternative perl
DIR3=$(echo SomeString | perl -ple 's/(.)/\l$1/')
DIR3=$(echo SomeString | perl -nle 'print lcfirst')
DIR3=$(echo "$DIR" | perl -ple 's/.*/lcfirst/e'
some terrible solutions;
DIR4=$(echo "$DIR" | sed 's/^\(.\).*/\1/' | tr "[A-Z]" "[a-z]")$(echo "$DIR" | sed 's/^.//')
DIR5=$(echo "$DIR" | cut -c1 | tr '[[:upper:]]' '[[:lower:]]')$(echo "$DIR" | cut -c2-)
All the above is tested with OSX's /bin/bash.
With sed:
var="SomeString"
echo $var | sed 's/^./\L&/'
^ means the start of the line
\L is the command to make the match in lowercase
& is the whole match
Perl solution:
DIR=SomeString
perl -le 'print lcfirst shift' "$DIR"
Since awk hasn't yet been mentioned, here's another way you could do it (requires GNU awk):
dir="SomeString"
new_dir=$(awk 'BEGIN{FS=OFS=""}{$1=tolower($1)}1' <<<"$dir")
This sets the input and output field separators to an empty string, so each character is a field. The tolower function does what you think it does. 1 at the end prints the line. If your shell doesn't support <<< you can do echo "$dir" | awk ... instead.
If you are looking for a POSIX compliant solution then have a look at typeset.
var='SomeString'
typeset -lL1 b="$var"
echo "${b}${var#?}"
Output:
someString
The typeset command creates a special variable that is lowercase, left aligned and one char long. ${var#?} trims the first occurrence of pattern from the start of $var and ? matches a single
character.
How can I extract all the words from a file, every word on a single line?
Example:
test.txt
This is my sample text
Output:
This
is
my
sample
text
The tr command can do this...
tr [:blank:] '\n' < test.txt
This asks the tr program to replace white space with a new line.
The output is stdout, but it could be redirected to another file, result.txt:
tr [:blank:] '\n' < test.txt > result.txt
And here the obvious bash line:
for i in $(< test.txt)
do
printf '%s\n' "$i"
done
EDIT Still shorter:
printf '%s\n' $(< test.txt)
That's all there is to it, no special (pathetic) cases included (And handling multiple subsequent word separators / leading / trailing separators is by Doing The Right Thing (TM)). You can adjust the notion of a word separator using the $IFS variable, see bash manual.
The above answer doesn't handle multiple spaces and such very well. An alternative would be
perl -p -e '$_ = join("\n",split);' test.txt
which would. E.g.
esben#mosegris:~/ange/linova/build master $ echo "test test" | tr [:blank:] '\n'
test
test
But
esben#mosegris:~/ange/linova/build master $ echo "test test" | perl -p -e '$_ = join("\n",split);'
test
test
This might work for you:
# echo -e "this is\tmy\nsample text" | sed 's/\s\+/\n/g'
this
is
my
sample
text
perl answer will be :
pearl.214> cat file1
a b c d e f pearl.215> perl -p -e 's/ /\n/g' file1
a
b
c
d
e
f
pearl.216>
Suppose I have the string 1:2:3:4:5 and I want to get its last field (5 in this case). How do I do that using Bash? I tried cut, but I don't know how to specify the last field with -f.
You can use string operators:
$ foo=1:2:3:4:5
$ echo ${foo##*:}
5
This trims everything from the front until a ':', greedily.
${foo <-- from variable foo
## <-- greedy front trim
* <-- matches anything
: <-- until the last ':'
}
Another way is to reverse before and after cut:
$ echo ab:cd:ef | rev | cut -d: -f1 | rev
ef
This makes it very easy to get the last but one field, or any range of fields numbered from the end.
It's difficult to get the last field using cut, but here are some solutions in awk and perl
echo 1:2:3:4:5 | awk -F: '{print $NF}'
echo 1:2:3:4:5 | perl -F: -wane 'print $F[-1]'
Assuming fairly simple usage (no escaping of the delimiter, for example), you can use grep:
$ echo "1:2:3:4:5" | grep -oE "[^:]+$"
5
Breakdown - find all the characters not the delimiter ([^:]) at the end of the line ($). -o only prints the matching part.
You could try something like this if you want to use cut:
echo "1:2:3:4:5" | cut -d ":" -f5
You can also use grep try like this :
echo " 1:2:3:4:5" | grep -o '[^:]*$'
One way:
var1="1:2:3:4:5"
var2=${var1##*:}
Another, using an array:
var1="1:2:3:4:5"
saveIFS=$IFS
IFS=":"
var2=($var1)
IFS=$saveIFS
var2=${var2[#]: -1}
Yet another with an array:
var1="1:2:3:4:5"
saveIFS=$IFS
IFS=":"
var2=($var1)
IFS=$saveIFS
count=${#var2[#]}
var2=${var2[$count-1]}
Using Bash (version >= 3.2) regular expressions:
var1="1:2:3:4:5"
[[ $var1 =~ :([^:]*)$ ]]
var2=${BASH_REMATCH[1]}
$ echo "a b c d e" | tr ' ' '\n' | tail -1
e
Simply translate the delimiter into a newline and choose the last entry with tail -1.
Using sed:
$ echo '1:2:3:4:5' | sed 's/.*://' # => 5
$ echo '' | sed 's/.*://' # => (empty)
$ echo ':' | sed 's/.*://' # => (empty)
$ echo ':b' | sed 's/.*://' # => b
$ echo '::c' | sed 's/.*://' # => c
$ echo 'a' | sed 's/.*://' # => a
$ echo 'a:' | sed 's/.*://' # => (empty)
$ echo 'a:b' | sed 's/.*://' # => b
$ echo 'a::c' | sed 's/.*://' # => c
There are many good answers here, but still I want to share this one using basename :
basename $(echo "a:b:c:d:e" | tr ':' '/')
However it will fail if there are already some '/' in your string.
If slash / is your delimiter then you just have to (and should) use basename.
It's not the best answer but it just shows how you can be creative using bash commands.
If your last field is a single character, you could do this:
a="1:2:3:4:5"
echo ${a: -1}
echo ${a:(-1)}
Check string manipulation in bash.
Using Bash.
$ var1="1:2:3:4:0"
$ IFS=":"
$ set -- $var1
$ eval echo \$${#}
0
echo "a:b:c:d:e"|xargs -d : -n1|tail -1
First use xargs split it using ":",-n1 means every line only have one part.Then,pring the last part.
Regex matching in sed is greedy (always goes to the last occurrence), which you can use to your advantage here:
$ foo=1:2:3:4:5
$ echo ${foo} | sed "s/.*://"
5
A solution using the read builtin:
IFS=':' read -a fields <<< "1:2:3:4:5"
echo "${fields[4]}"
Or, to make it more generic:
echo "${fields[-1]}" # prints the last item
for x in `echo $str | tr ";" "\n"`; do echo $x; done
improving from #mateusz-piotrowski and #user3133260 answer,
echo "a:b:c:d::e:: ::" | tr ':' ' ' | xargs | tr ' ' '\n' | tail -1
first, tr ':' ' ' -> replace ':' with whitespace
then, trim with xargs
after that, tr ' ' '\n' -> replace remained whitespace to newline
lastly, tail -1 -> get the last string
For those that comfortable with Python, https://github.com/Russell91/pythonpy is a nice choice to solve this problem.
$ echo "a:b:c:d:e" | py -x 'x.split(":")[-1]'
From the pythonpy help: -x treat each row of stdin as x.
With that tool, it is easy to write python code that gets applied to the input.
Edit (Dec 2020):
Pythonpy is no longer online.
Here is an alternative:
$ echo "a:b:c:d:e" | python -c 'import sys; sys.stdout.write(sys.stdin.read().split(":")[-1])'
it contains more boilerplate code (i.e. sys.stdout.read/write) but requires only std libraries from python.