1, file descriptor -e Determine whether the object exists
-d Determine whether the object exists and is a directory
-f Determine whether the object exists, and it is a regular file
-L Determine
Tag: is there
Regular expression – check if there is only space in the string
How to check if there are only spaces in a string?
I want to use conditions in an if() statement.
For example,
str<-" "< br />#check if str has only white spaces? example usage
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