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C Library Functions  - scratch (3)

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NAME

scratch(3f) - [M_io:QUERY] Return the name of a scratch file (LICENSE:PD)

CONTENTS

Synopsis
Description
Options
Example
Author
License

SYNOPSIS

function scratch(prefix) result(tname)

     character(len=:),allocatable         :: tname
     character(len=*),intent(in),optional :: prefix

DESCRIPTION

Fortran supports non-retainable scratch files via OPEN(STATUS=’SCRATCH’,...) . There are circumstances where a file with a unique name is required instead. Specifying the pathname of a file can be required for performance reasons, file space limitations, or to support the ability for other processes or subprocesses to access the file.

SCRATCH(3f) Return the name of a scratch file in the scratch directory set by the most common environment variables used to designate a scratch directory unless the prefix contains the character "/" or "\".

$TMPDIR is the canonical environment variable in Unix and POSIX[1] used to specify a temporary directory for scratch space. If $TMPDIR is not set, $TEMP, $TEMPDIR, and $TMP are examined in that order. If nothing is set "/tmp/" is used.

OPTIONS

prefix

an optional prefix for the leaf of the filename. A suffix created by genuuid(3) is used to make the name unique. The prefix is used as-is if it contains the character "/" or "\". Otherwise, the prefix is prefixed by the first value that is not blank from the set {$TMPDIR, $TEMP, $TEMPDIR, $TMP, /tmp}. The default prefix is the basename of the program that called the procedure (the name trimmed of directories and anything from the right-most period in the name to the end of the name).

EXAMPLE

Sample:

    program demo_scratch
    use M_io, only : scratch
    implicit none
    write(*,*)’find good scratch file name candidates; one should test if writable’
    call printit(’JUNK:’)
    call printit(’./’)
    call printit(’/var/tmp/’)
    call printit(’’)
    call printit()
    contains
    subroutine printit(NAME)
    character(len=*),intent(in),optional :: NAME
    if(present(NAME))then
       write(*,’(a,t20,a)’)NAME,scratch(NAME)
    else
       write(*,’(a,t20,a)’)’*NOT PRESENT*’,scratch()
    endif
    end subroutine printit
    end program demo_scratch

Results:

   >  find good scratch file name candidates; one should test if writable
   > JUNK:              /tmp/JUNK:405d766e-1320-4405-50e1-5d88fffbee9a.scr
   > ./                 ./xx-901606b1-6ad2-4e96-6b17-e8bffedf2452.scr
   > /var/tmp/          /var/tmp/xx-3f5c55fa-17ca-4020-4a05-a9d9cfad8dbe.scr
   >                    /tmp/f10e0491-a2ff-4455-5ff6-55d7dfe7fa8c.scr
   > *NOT PRESENT*      /tmp/xx-f4fed5f7-3694-4609-5af4-8902ffa75839.scr

AUTHOR

John S. Urban

LICENSE

Public Domain

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Nemo Release 3.1

scratch (3)

July 22, 2023

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