Input-Files.html 5.9 KB

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  14. <title>Using as: Input Files</title>
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  57. <a name="Input-Files"></a>
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  60. Next: <a href="Object.html#Object" accesskey="n" rel="next">Object</a>, Previous: <a href="Command-Line.html#Command-Line" accesskey="p" rel="prev">Command Line</a>, Up: <a href="Overview.html#Overview" accesskey="u" rel="up">Overview</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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  62. <hr>
  63. <a name="Input-Files-1"></a>
  64. <h3 class="section">1.5 Input Files</h3>
  65. <a name="index-input"></a>
  66. <a name="index-source-program"></a>
  67. <a name="index-files_002c-input"></a>
  68. <p>We use the phrase <em>source program</em>, abbreviated <em>source</em>, to
  69. describe the program input to one run of <code>as</code>. The program may
  70. be in one or more files; how the source is partitioned into files
  71. doesn&rsquo;t change the meaning of the source.
  72. </p>
  73. <p>The source program is a concatenation of the text in all the files, in the
  74. order specified.
  75. </p>
  76. <p>Each time you run <code>as</code> it assembles exactly one source
  77. program. The source program is made up of one or more files.
  78. (The standard input is also a file.)
  79. </p>
  80. <p>You give <code>as</code> a command line that has zero or more input file
  81. names. The input files are read (from left file name to right). A
  82. command line argument (in any position) that has no special meaning
  83. is taken to be an input file name.
  84. </p>
  85. <p>If you give <code>as</code> no file names it attempts to read one input file
  86. from the <code>as</code> standard input, which is normally your terminal. You
  87. may have to type <tt class="key">ctl-D</tt> to tell <code>as</code> there is no more program
  88. to assemble.
  89. </p>
  90. <p>Use &lsquo;<samp>--</samp>&rsquo; if you need to explicitly name the standard input file
  91. in your command line.
  92. </p>
  93. <p>If the source is empty, <code>as</code> produces a small, empty object
  94. file.
  95. </p>
  96. <a name="Filenames-and-Line_002dnumbers"></a>
  97. <h4 class="subheading">Filenames and Line-numbers</h4>
  98. <a name="index-input-file-linenumbers"></a>
  99. <a name="index-line-numbers_002c-in-input-files"></a>
  100. <p>There are two ways of locating a line in the input file (or files) and
  101. either may be used in reporting error messages. One way refers to a line
  102. number in a physical file; the other refers to a line number in a
  103. &ldquo;logical&rdquo; file. See <a href="Errors.html#Errors">Error and Warning Messages</a>.
  104. </p>
  105. <p><em>Physical files</em> are those files named in the command line given
  106. to <code>as</code>.
  107. </p>
  108. <p><em>Logical files</em> are simply names declared explicitly by assembler
  109. directives; they bear no relation to physical files. Logical file names help
  110. error messages reflect the original source file, when <code>as</code> source
  111. is itself synthesized from other files. <code>as</code> understands the
  112. &lsquo;<samp>#</samp>&rsquo; directives emitted by the <code>gcc</code> preprocessor. See also
  113. <a href="File.html#File"><code>.file</code></a>.
  114. </p>
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