Extract file extension: Difference between revisions

Using this paraphrased Rosetta Code task's definition that:

a legal file extension   ''only''   consists of mixed-case Latin letters and/or decimal digits.

<lang rexx>/*REXX pgm extracts the file extension (defined above from the RC task) from a file name*/

@.= /*define default value for the @ array.*/

parse arg fID /*obtain any optional arguments from CL*/

if fID\=='' then @.1 = fID /*use the filename from the C.L. */

else do /*No filename given? Then use defaults.*/

do j=1 while @.j\==''; x= /*process (all of) the file name(s). */

p=lastpos(.,@.j) /*find the last position of a period. */

if p\==0 then x=substr(@.j, p+1) /*Found a dot? Then get stuff after it*/

if \datatype(x, 'A') then x= /*is it upper/lowercase letters|digits?*/

if x=='' then x= " [null]" /*use a better name for a "null". */

else x= . || x /*prefix the extension with a period. */

say 'file extension=' left(x, 20) "for file name=" @.j

end /*j*/ /*stick a fork in it, we're all done. */</lang>

'''output''' &nbsp; when using the default (internal) inputs:

file extension= .jpg for file name= picture.jpg

file extension= .png for file name= http://mywebsite.com/pictures/image.png

file extension= .longextension for file name= myuniquefile.longextension

file extension= [null] for file name= IAmAFileWithoutExtension

file extension= [null] for file name= /path/to.my/file

file extension= [null] for file name= file.odd_one