Unexpected newline / tabbing behaviour in write to string

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1

My compiler is GNU Fortran on Windows 10. Details at the bottom.

If I run this:

program tab_newline_problem_with_gfortran
  implicit none

  character(len=128) :: str

  write (str,101) ': This is the first line.'//NEW_LINE('A'), &
       '       '// &
       'This is the second line.'
101 format (A,A)

  stop str

end program tab_newline_problem_with_gfortran

then I get this:

STOP : This is the first line.
       This is the second line.

which is what I expect.

However, if I remove the leading whitespace string for the second output line and instead insert a T7 tab format specifier like this:

program tab_newline_problem_with_gfortran
  implicit none

  character(len=128) :: str

  write (str,101) ': This is the first line.'//NEW_LINE('A'), &
       'This is the second line.'
101 format (A,T7,A)

  stop str

end program tab_newline_problem_with_gfortran

then I get this unexpected output:

STOP : ThisThis is the second line.

In addition if, instead of using NEW_LINE(), I use the “/” newline format specifier, like this:

program tab_newline_problem_with_gfortran
  implicit none

  character(len=128) :: str

  write (str,101) ': This is the first line.', &
       'This is the second line.'
101 format (A,/,A)

  stop str

end program tab_newline_problem_with_gfortran

then I get this runtime error:

At line 7 of file tab_newline_problem_with_gfortran.f90
Fortran runtime error: End of file

Can someone please explain?

GNU Fortran (MinGW.org GCC-6.3.0-1) 6.3.0

OS Name:                   Microsoft Windows 10 Pro Education
OS Version:                10.0.19045 N/A Build 19045
System Model:              Latitude 3190
System Type:               x64-based PC
Processor(s):              1 Processor(s) Installed.
                           [01]: Intel64 Family 6 Model 122 Stepping 8 GenuineIntel ~1101 Mhz
BIOS Version:              Dell Inc. 1.15.2, 29/07/2021
2

Welcome to the forum!

The tab format specifier puts the writing position explicitly to a position relative to the start of the string (line).

The newline specifier introduces a new line, but for an internal write that would be the next element of a string array. It does not mean a new line character. Since your write statement involves a scalar, there is no next element and that gives the run-time error.

3

@Arjen Thank you. Very clear.