How can I automatically name files being exported based on input parameters

Question

I have Mathematica notebook that performs some operation say

a=2
b=3
c=5
d=4

how do I set the output file after evaluation to be named using the values $2,3,5,\ldots$

like "2_3_5_4_" such that the the naming automatically takes the values assigned to a,b,c d

Answer 1

Your data

{a, b, c, d} = RandomInteger[9, 4];
data = a b c d;

Exporting with nice file-names featuring date and variable values using StringTemplate

Export[
 StringTemplate[
  "Date`1`_Values_a`2`_b`3`_c`4`.txt"
  ][DateString[{"Year", "Month", "Day"}], a, b, c]
 , data]

"Date20141201_Values_a7_b5_c3.txt"

Or using ToString and StringJoin as suggested by @Kuba

 Export[
  StringJoin["Data_", ToString /@ Riffle[{a, b, c, d}, "_"], ".txt"]
 , data]

"Data_7_5_3_7.txt"

Answer 2

There is a simple way if you are using the Table[] function. For example: Table[Export[NotebookDirectory[]<>ToString@StringForm["test``.txt", l], Table[{l,l^2}, {l, 1, 10}];. In this case, the program will generate ten files written as "testl.txt" for each l with the values l and l^2 as columns.