118 lines
7.9 KiB
HTML
118 lines
7.9 KiB
HTML
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="File systems" />
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<meta name="abstract" content="i5/OS PASE programs can access any file or resource that is accessible through the integrated file system, including objects in the QSYS.LIB and QOPT file systems." />
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<meta name="description" content="i5/OS PASE programs can access any file or resource that is accessible through the integrated file system, including objects in the QSYS.LIB and QOPT file systems." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2000, 2006" />
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<title>File systems</title>
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</head>
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<body id="rzalffilesystems"><a name="rzalffilesystems"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">File systems</h1>
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<div><p><span class="keyword">i5/OS™</span> PASE programs
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can access any file or resource that is accessible through the integrated
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file system, including objects in the QSYS.LIB and QOPT file systems.</p>
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<div class="section"><h4 class="sectiontitle">Buffered input and output</h4><p>Input
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and output to and from external devices is buffered on <span class="keyword">i5/OS</span>;
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it is handled by input and output processors that deal with blocks of data.
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Conversely, operating systems, such as AIX<sup>®</sup> and Linux<sup>®</sup>, typically operate with character-by-character
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(unbuffered) input and output. On <span class="keyword">i5/OS</span>,
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only certain input and output signals (for example, the Enter key, function
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keys, and system request) send an interrupt to the system.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Data conversion support</h4><p><span class="keyword">i5/OS</span> PASE programs pass ASCII (or
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UTF-8) path names to the <span class="apiname">open()</span> function to open byte stream
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files, where the name is automatically converted to the encoding scheme used
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by <span class="keyword">i5/OS</span>, but any data
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read or written from the open file is not converted.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Use of file descriptors</h4><p>The <span class="keyword">i5/OS</span> PASE run time normally uses
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ILE C run time support for files stdin, stdout, and stderr, which provide
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consistent behavior for <span class="keyword">i5/OS</span> PASE
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and ILE programs.</p>
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</div>
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<div class="section"><p><span class="keyword">i5/OS</span> PASE
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and ILE C use the same streams for standard input and output (stdin, stdout,
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and stderr). <span class="keyword">i5/OS</span> PASE
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programs always access standard input and output using file descriptors 0,
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1, and 2. ILE C, however, does not always use integrated file descriptors
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for stdin, stdout, and stderr, so <span class="keyword">i5/OS</span> PASE
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provides a mapping between <span class="keyword">i5/OS</span> PASE
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file descriptors and descriptors in the integrated file system. Because of
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this mapping, <span class="keyword">i5/OS</span> PASE
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programs and ILE C programs can use different descriptor numbers to access
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the same open file.</p>
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<p>You can use the <span class="keyword">i5/OS</span> PASE
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extension on the <tt>fcntl</tt> function, F_MAP_XPFFD, to assign an <span class="keyword">i5/OS</span> PASE descriptor to an ILE
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number. This is useful if your <span class="keyword">i5/OS</span> PASE
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application needs to do file operations for an ILE descriptor that was not
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created by <span class="keyword">i5/OS</span> PASE.</p>
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<p>An i5/OS system-unique
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extension to the <span class="apiname">fstatx()</span> function, STX_XPFFD_PASE, allows
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an <span class="keyword">i5/OS</span> PASE program to
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determine the integrated file system descriptor number for an <span class="keyword">i5/OS</span> PASE
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file descriptor. Special values (negative numbers) are returned for any <span class="keyword">i5/OS</span> PASE descriptor attached to
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ILE C runtime support for files stdin, stdout, and stderr.</p>
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<p>If the ILE
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environment variable QIBM_USE_DESCRIPTOR_STDIO is set to Y or I when the Qp2RunPase()
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API is called, <span class="keyword">i5/OS</span> PASE
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synchronizes file descriptors 0, 1, and 2 with the integrated file system
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so that both <span class="keyword">i5/OS</span> PASE
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and ILE C programs use the same descriptor numbers for files stdin, stdout,
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and stderr. When operating in this mode, if either <span class="keyword">i5/OS</span> PASE
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code or ILE C code closes or reopens file descriptor 0, 1, or 2, the change
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affects stdin, stdout, and stderr processing for both environments.</p>
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<p><span class="keyword">i5/OS</span> PASE run time generally does
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no character encoding conversion for data read or written through <span class="keyword">i5/OS</span> PASE file descriptors (including
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sockets), except that ASCII-to-EBCDIC conversion is done (between the <span class="keyword">i5/OS</span> PASE CCSID and job default
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CCSID) for data read from ILE C stdin or written to ILE C stdout and stderr.</p>
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<p>Two
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environment variables control the automatic translation of stdin, stdout,
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and stderr:</p>
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<ul><li>The variable that generally applies is QIBM_USE_DESCRIPTOR_STDIO. When
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set to Y, the ILE runtime uses file descriptor 0, 1, or 2 for these files.</li>
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<li>The <span class="keyword">i5/OS</span> PASE
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system-specific environment variable is QIBM_PASE_DESCRIPTOR_STDIO. It has
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values of B for binary and T for text.</li>
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</ul>
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<p>ASCII-to-EBCDIC conversion for <span class="keyword">i5/OS</span> PASE
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stdin, stdout, and stderr is disabled if the ILE environment variable QIBM_USE_DESCRIPTOR_STDIO
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is set to Y and QIBM_PASE_DESCRIPTOR_STDIO is set to B (allowing binary data
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to be read from stdin and written to stdout or stderr). The default for QIBM_PASE_DESCRIPTOR_STDIO
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is T for text. This value causes translation of EBCDIC to ASCII.</p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalfinteract.htm" title="As you customize your i5/OS PASE programs to use i5/OS functions, you need to consider the ways in which your program will interact with them.">How i5/OS PASE programs interact with i5/OS</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rzalfdataconv.htm" title="Most operating systems, such as AIX and Linux, use ASCII character encoding. Most i5/OS functions use EBCDIC character encoding. You can specify a coded character set identifier (CCSID) value for some i5/OS object types to identify a specific encoding for character data in the object.">Data encoding</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../ifs/rzaaxkickoff.htm">Integrated file system</a></div>
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</div>
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</div>
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</body>
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</html>
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