Remove everything after space in string

问题

I would like to remove everything after a space in a string.

For example:

"my string is sad"

should return

"my"

I've been trying to figure out how to do this using sub/gsub but have been unsuccessful so far.

回答1:

strsplit("my string is sad"," ")[[1]][1]

回答2:

or, substitute everything behind the first space to nothing:

gsub(' [A-z ]*', '' , 'my string is sad')

And with numbers:

gsub('([0-9]+) .*', '\\1', c('c123123123 0320.1'))

回答3:

You may use a regex like

sub(" .*", "", x)

See the regex demo.

Here, sub will only perform a single search and replace operation, the .* pattern will find the first space (since the regex engine is searching strings from left to right) and .* matches any zero or more characters (in TRE regex flavor, even including line break chars, beware when using perl=TRUE, then it is not the case) as many as possible, up to the string end.

Some variations:

sub("[[:space:]].*", "", x) # \s or [[:space:]] will match more whitespace chars
sub("(*UCP)(?s)\\s.*", "", x, perl=TRUE) # PCRE Unicode-aware regex
stringr::str_replace(x, "(?s) .*", "")   # (?s) will force . to match any chars

See the online R demo.

回答4:

If you want to do it with a regex:

gsub('([A-z]+) .*', '\\1', 'my string is sad')

来源：https://stackoverflow.com/questions/9319242/remove-everything-after-space-in-string