StringiFor Documentation

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Basic I/O ​

The string type integrates with Fortran's I/O system through defined write/read type-bound procedures and operator overloading.

Importing ​

fortran
use stringifor

This brings in the string type and all overloaded operators and built-in replacements.

Assigning and Printing ​

The simplest way to create a string is by assigning a character literal:

fortran
type(string) :: s

s = 'Hello World'

There are three equivalent ways to print it:

fortran
! 1. chars() returns a standard character variable
print "(A)", s%chars()

! 2. Defined I/O (requires GFortran >= 7.1 for DT descriptor)
print "(DT)", s

! 3. Concatenation with '' triggers automatic conversion to character
print "(A)", s//''

TIP

The //'' idiom is the most portable and concise way to pass a string wherever a character is expected. The concatenation operator // is overloaded to return a standard character, enabling seamless integration with any Fortran procedure expecting a character argument.

Reading from Standard Input ​

fortran
type(string) :: s

read *, s

Reading from a File ​

Line by line ​

fortran
type(string) :: line
integer      :: unit, iostat

open(newunit=unit, file='data.txt', status='OLD')
do
  call line%read_line(unit=unit, iostat=iostat)
  if (iostat /= 0) exit
  ! process line...
end do
close(unit)

All lines at once ​

fortran
type(string), allocatable :: lines(:)

call read_file(file='data.txt', lines=lines)
! lines(1), lines(2), ... contain each line

Entire file as a single stream ​

fortran
type(string) :: content

call content%read_file(file='data.txt')

Writing to a File ​

fortran
type(string) :: lines(3)

lines(1) = 'First line'
lines(2) = 'Second line'
lines(3) = 'Third line'

call write_file(file='output.txt', lines=lines)

Unformatted (Binary) I/O ​

Both read_file / write_file accept an optional form='unformatted' argument. Only access='stream' with new_line as line terminator is supported:

fortran
type(string), allocatable :: lines(:)

call read_file(file='data.bin', lines=lines, form='unformatted')
call write_file(file='data.bin', lines=lines, form='unformatted')

Checking Allocation ​

fortran
type(string) :: s

if (s%is_allocated()) then
  print "(A)", s%chars()
end if

Freeing Memory ​

fortran
call s%free()