Parsing command line arguments as strings to store integer in Fortran

Question

I am following a Fortran tutorial, however the below code does not seem to work. I am trying to read a 2 digit number from command line, however I get the error UNIT specification at "TRIM(buffer)" must be an INTEGER expression or a CHARACTER variable.

INTEGER :: number
CHARACTER(LEN=20) :: buffer

buffer = ""
CALL GET_COMMAND_ARGUMENT(1, buffer)
READ(TRIM(buffer), FMT="(I2)") number

So the issue as I understand it, is that READ is not sure that the output of TRIM will return a CHARACTER value. Can I somehow declare that it is a CHARACTER or is there another way of getting around this issue?

For what it is worth I am using gfortran.

francescalus · Accepted Answer · 2014-07-30 16:17:44Z

3

TRIM(buffer) indeed returns a character value. This is, however, an expression and not a variable. As the error message suggests, an expression is fine for giving a unit number, but in the case of reading from a character, a variable is required.

As TRIM will act merely to provide a value with the trailing spaces stripped from buffer, this isn't needed: the spaces won't affect the reading. Instead, just go for

read(buffer, '(I2)') number

or even

read(buffer(1:2), '(I2)') number

More generally, a more complicated character expression can be assigned to a variable and this latter variable used in the read context.

edited Jul 30, 2014 at 16:17

answered Jul 30, 2014 at 16:05

francescalus

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