Define the file path from the file name in R

问题

I know that I can find file name from full file path in R, but is there a way to define the path to the file just from the file name? Think about such scenario: you store the data file in the cloud (e.g. Dropbox) so the path for this file is slightly different at your home: read.table("path/user1/data.dat") and work: read.table("path/user2/data.dat"). Therefore, every time you want to read.table() you have to change one element of the path to match either you work or home path (on Mac OS X it's specifically the User part of the path that you need to change). I was wondering whether it's possible to make R to automatically detect such change in the path (e.g. different User) or detect the path to the file just from the name of this file.

回答1:

You can access the environment variables with Sys.getenv().

Here is a short extract from the results on my machine:

Sys.getenv()

...
USERNAME 
"Andrie" 
USERPROFILE 
"C:\\Users\\Andrie" 
windir 
"C:\\Windows"

You can extract individual elements by including the name of that element in the call:

> Sys.getenv("USERNAME")
[1] "Andrie"

---

If you can identify in these variables exactly what it is you need, you can then construct your file path using file.path

---

For more information on the environment variables, and some system-specific exceptions, see ?Sys.getenv

来源：https://stackoverflow.com/questions/8355762/define-the-file-path-from-the-file-name-in-r