If I have a string that looks like this:
"this_is_the_string"
Inside a bash script, I would like to convert it to PascalCase, ie UpperCamelCase to look like this:
"ThisIsTheString"
I found that converting to lowerCamelCase can be done like this:
"this_is_the_string" | sed -r 's/([a-z]+)_([a-z])([a-z]+)/1U2L3/'
Unfortunately I am not familiar enough with regexes to modify this.
Answers:
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Method 1
$ echo "this_is_the_string" | sed -r 's/(^|_)([a-z])/U2/g' ThisIsTheString
Substitute pattern
(^|_) at the start of the string or after an underscore – first group
([a-z]) single lower case letter – second group
by
U2 uppercasing second group
g globally.
Method 2
Here’s a Perl way:
$ echo "this_is_the_string" | perl -pe 's/(^|_)./uc($&)/ge;s/_//g' ThisIsTheString
It can deal with strings of arbitrary length:
$ echo "here_is_another_larger_string_with_more_parts" |
perl -pe 's/(^|_)./uc($&)/ge;s/_//g'
HereIsAnotherLargerStringWithMoreParts
It will match any character (.) that comes after either the start of the string or an underscore ((^|_)) and replace it with the upper case version of itself (uc($&)). The $& is a special variable that contains whatever was just matched. The e at the end of s///ge allows the use of expressions (the uc() function in this case) within the substitution and the g makes it replace all occurrences in the line. The second substitution removes the underscores.
Method 3
Since you’re using bash, if you stored your string in a variable you could also do it shell-only:
uscore="this_is_the_string_to_be_converted"
arr=(${uscore//_/ })
printf %s "${arr[@]^}"
ThisIsTheStringToBeConverted
${uscore//_/ } replaces all _ with space, (....) splits the string into an array, ${arr[@]^} converts the first letter of each element to upper case and then printf %s .. prints all elements one after another.
You can store the camel-cased string into another variable:
printf -v ccase %s "${arr[@]^}"
and use/reuse it later, e.g.:
printf %s\n $ccase ThisIsTheStringToBeConverted
Or, with zsh:
uscore="this_is_the_string_to_be_converted"
arr=(${(s:_:)uscore})
printf %s "${(C)arr}"
ThisIsTheStringToBeConverted
(${(s:_:)uscore}) splits the string on _ into an array, (C) capitalizes the first letter of each element and printf %s ... prints all elements one after another..
To store it in another variable you could use (j::) to joins the elements:
ccase=${(j::)${(C)arr}}
and use/reuse it later:
printf %s\n $ccase ThisIsTheStringToBeConverted
Method 4
It is not necessary to represent the entire string in a regular expression match — sed has the /g modifier that allows you to walk over multiple matches and replace each of them:
echo "this_is_the_string" | sed 's/_([a-z])/U1/g;s/^([a-z])/U1/g'
The first regex is _([a-z]) — each letter after underscore; the second one matches the first letter in a string.
Method 5
I only put in this answer because it is shorter and simpler than any other so far.
sed -re "s~(^|_)(.)~U2~g"
It says: upcase, the character following a _ or the start. Non letters will not be changed, as they have no case.
Method 6
In perl:
$ echo 'alert_beer_core_hemp' | perl -pe 's/(?:b|_)(p{Ll})/u$1/g'
AlertBeerCoreHemp
This is also i18n-able:
$ echo 'алерт_беер_коре_хемп' | perl -CIO -pe 's/(?:b|_)(p{Ll})/u$1/g'
АлертБеерКореХемп
Method 7
I did it this way:
echo "this_is_the_string" | sed -r 's/(<|_)([[:alnum:]])/U2/g'
and got this result:
ThisIsTheString
Method 8
My choice is:
echo "this_is-the_string-2.0" | perl -pe 's/(?:^|[^a-z])([a-z0-9])/u$1/g'
Which results in:
ThisIsTheString20
All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0