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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gfortran/File-format-of-unformatted-sequential-files.html | |
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diff --git a/share/doc/gfortran/File-format-of-unformatted-sequential-files.html b/share/doc/gfortran/File-format-of-unformatted-sequential-files.html new file mode 100644 index 0000000..aacf5b1 --- /dev/null +++ b/share/doc/gfortran/File-format-of-unformatted-sequential-files.html @@ -0,0 +1,146 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1999-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>The GNU Fortran Compiler: File format of unformatted sequential files</title> + +<meta name="description" content="The GNU Fortran Compiler: File format of unformatted sequential files"> +<meta name="keywords" content="The GNU Fortran Compiler: File format of unformatted sequential files"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Compiler-Characteristics.html#Compiler-Characteristics" rel="up" title="Compiler Characteristics"> +<link href="Asynchronous-I_002fO.html#Asynchronous-I_002fO" rel="next" title="Asynchronous I/O"> +<link href="File-operations-on-symbolic-links.html#File-operations-on-symbolic-links" rel="previous" title="File operations on symbolic links"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="File-format-of-unformatted-sequential-files"></a> +<div class="header"> +<p> +Next: <a href="Asynchronous-I_002fO.html#Asynchronous-I_002fO" accesskey="n" rel="next">Asynchronous I/O</a>, Previous: <a href="File-operations-on-symbolic-links.html#File-operations-on-symbolic-links" accesskey="p" rel="previous">File operations on symbolic links</a>, Up: <a href="Compiler-Characteristics.html#Compiler-Characteristics" accesskey="u" rel="up">Compiler Characteristics</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="File-format-of-unformatted-sequential-files-1"></a> +<h3 class="section">4.9 File format of unformatted sequential files</h3> +<a name="index-file_002c-unformatted-sequential"></a> +<a name="index-unformatted-sequential"></a> +<a name="index-sequential_002c-unformatted"></a> +<a name="index-record-marker"></a> +<a name="index-subrecord"></a> + +<p>Unformatted sequential files are stored as logical records using +record markers. Each logical record consists of one of more +subrecords. +</p> +<p>Each subrecord consists of a leading record marker, the data written +by the user program, and a trailing record marker. The record markers +are four-byte integers by default, and eight-byte integers if the +<samp>-fmax-subrecord-length=8</samp> option (which exists for backwards +compability only) is in effect. +</p> +<p>The representation of the record markers is that of unformatted files +given with the <samp>-fconvert</samp> option, the <a href="CONVERT-specifier.html#CONVERT-specifier">CONVERT specifier</a> +in an open statement or the <a href="GFORTRAN_005fCONVERT_005fUNIT.html#GFORTRAN_005fCONVERT_005fUNIT">GFORTRAN_CONVERT_UNIT</a> environment +variable. +</p> +<p>The maximum number of bytes of user data in a subrecord is 2147483639 +(2 GiB - 9) for a four-byte record marker. This limit can be lowered +with the <samp>-fmax-subrecord-length</samp> option, although this is +rarely useful. If the length of a logical record exceeds this limit, +the data is distributed among several subrecords. +</p> +<p>The absolute of the number stored in the record markers is the number +of bytes of user data in the corresponding subrecord. If the leading +record marker of a subrecord contains a negative number, another +subrecord follows the current one. If the trailing record marker +contains a negative number, then there is a preceding subrecord. +</p> +<p>In the most simple case, with only one subrecord per logical record, +both record markers contain the number of bytes of user data in the +record. +</p> +<p>The format for unformatted sequential data can be duplicated using +unformatted stream, as shown in the example program for an unformatted +record containing a single subrecord: +</p> +<div class="smallexample"> +<pre class="smallexample">program main + use iso_fortran_env, only: int32 + implicit none + integer(int32) :: i + real, dimension(10) :: a, b + call random_number(a) + open (10,file='test.dat',form='unformatted',access='stream') + inquire (iolength=i) a + write (10) i, a, i + close (10) + open (10,file='test.dat',form='unformatted') + read (10) b + if (all (a == b)) print *,'success!' +end program main +</pre></div> + +<hr> +<div class="header"> +<p> +Next: <a href="Asynchronous-I_002fO.html#Asynchronous-I_002fO" accesskey="n" rel="next">Asynchronous I/O</a>, Previous: <a href="File-operations-on-symbolic-links.html#File-operations-on-symbolic-links" accesskey="p" rel="previous">File operations on symbolic links</a>, Up: <a href="Compiler-Characteristics.html#Compiler-Characteristics" accesskey="u" rel="up">Compiler Characteristics</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |