Add space before uppercase letter

Question

I have a strings:

AddData
TestSomething
TellMeWhoYouAre

and so on. I want to add space before uppercase letters. How can I do it?

Answer 1

Using sed, and assuming you don't want a space in front of the word:

$ sed 's/\([^[:blank:]]\)\([[:upper:]]\)/\1 \2/g' file.in
Add Data
Test Something
Tell Me Who You Are

The substitution will look for an upper-case letter immediately following a another non-whitespace character, and insert a space in-between the two.

For strings with more than one consecutive upper-case character, like WeAreATeam, this produces We Are ATeam. To sort this, run the substitution a second time:

$ sed -e 's/\([^[:blank:]]\)\([[:upper:]]\)/\1 \2/g' \
      -e 's/\([^[:blank:]]\)\([[:upper:]]\)/\1 \2/g' file.in

Answer 2

Perl, using lookbehind and lookahead zero-width regular expressions:

$ perl -pe 's/(?<=\w)(?=[A-Z])/ /g'  file.in 

Tell Me Who You Are                    ## TellMeWhoYouAre
I Am A Regular Expression User         ## IAmARegulaExpressionUser

This version is also separating consecutive uppercase letters.

Answer 3

sed -r -e "s/([^A-Z])([A-Z])/\1 \2/g"

Add space between a letter that is not an upper-case letter and a letter that is an upper-case letter

Answer 4

Came here to get this question answered and, after reading the other suggestions, arrived at a solution that handles the ReadFromUSBDrive to Read From USB Drive case, too - I adapted ka3ak's expression style and kusalananda's use of multiple expressions to get the following:

 sed -r -e "s/([^A-Z])([A-Z])/\1 \2/g" -e "s/([A-Z]+)([A-Z])/\1 \2/g" file.in

e.g.

$ sed -r -e "s/([^A-Z])([A-Z])/\1 \2/g" -e "s/([A-Z]+)([A-Z])/\1 \2/g" <<EOF
AddData
TestSomething
TellMeWhoYouAre
ReadFromUSBDrive
EOF
Add Data
Test Something
Tell Me Who You Are
Read From USB Drive

Note that this will choke on single-letter words like the article "A" or the pronoun "I" when they occur directly before an abbreviation as they would be indistinguishable from the characters in an intended abbreviation, e.g. ReadAUSBDrive will render Read AUSB Drive.

Answer 5

Python solution:

#!/usr/bin/env python
from __future__ import print_function
import sys

with open(sys.argv[1]) as f:
    for line in f:
        for char in line:
            if char.isupper():
               print(" "+char,end="")
            else:
               print(char,end="")

Test run:

$ ./add_space_to_upper.py input.txt                        
 Add Data
 Test Something
 Tell Me Who You Are

Answer 6

Using Raku (formerly known as Perl_6)

Sample Input:

AddData
TestSomething
TellMeWhoYouAre
IClimbALadder
ReadFileFromCDDrive
ReadAUSBDrive

Code and Output (1):

raku -pe 's:g/(<?after <:Ll> >) (<?before <:Lu>+ >)/ /;' 

Add Data
Test Something
Tell Me Who You Are
IClimb ALadder
Read File From CDDrive
Read AUSBDrive

Code and Output (2):

raku -pe 's:g/(<?after <:L> >) (<?before <:Lu>+ >)/ /;' 

Add Data
Test Something
Tell Me Who You Are
I Climb A Ladder
Read File From C D Drive
Read A U S B Drive

Above is a pretty direct translation of @JJoao's Perl5 code. The <:L>, <:Ll>, and <:Lu> represent "Unicode letter", "Unicode letter-lower", and `Unicode letter-upper", respectively.

Addendum: Like others in this thread have noted, it appears that sequential s/// substitution calls can get you closer to a desired output. Below, take the results of the first Raku example (above), and run a second s/// substitution:

Code and Output (3):

raku -pe 's:g/(<?after <:Ll> >) (<?before <:Lu> >)/ /;'  | perl6 -pe 's:g/(<?after <:Lu>+ >) (<?before <:Lu><:Ll>+ >)/ /;'

Add Data
Test Something
Tell Me Who You Are
I Climb A Ladder
Read File From CD Drive
Read AUSB Drive

The results with Raku (5/6 test lines separated correctly), equals the best results obtained with other languages posted thus far.

http://raku.org