1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
|
<!DOCTYPE html>
<html lang="en" data-content_root="../">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" /><meta name="viewport" content="width=device-width, initial-scale=1" />
<title>psub - perform process substitution — fish-shell 4.2.1 documentation</title>
<link rel="stylesheet" type="text/css" href="../_static/pygments.css?v=4da8bbd6" />
<link rel="stylesheet" type="text/css" href="../_static/pydoctheme.css?v=f89b4716" />
<script src="../_static/documentation_options.js?v=6fb65176"></script>
<script src="../_static/doctools.js?v=9bcbadda"></script>
<script src="../_static/sphinx_highlight.js?v=dc90522c"></script>
<link rel="index" title="Index" href="../genindex.html" />
<link rel="search" title="Search" href="../search.html" />
<link rel="next" title="pushd - push directory to directory stack" href="pushd.html" />
<link rel="prev" title="prompt_pwd - print pwd suitable for prompt" href="prompt_pwd.html" />
<link rel="shortcut icon" type="image/png" href="../_static/fish.png" />
</head><body><div id="fmain">
<div class="related" role="navigation" aria-label="Related">
<h3>Navigation</h3>
<ul>
<li><img src="../_static/fish.png" alt=""
style="width: 80px; height: 80px; vertical-align: middle; margin-top: -1px"/></li>
<li><a href="https://fishshell.com/">fish-shell</a> »</li>
<a href="../index.html">fish-shell 4.2.1 documentation</a> »
<li class="nav-item nav-item-1"><a href="../commands.html" accesskey="U">Commands</a> »</li>
<li class="nav-item nav-item-this"><a href="">psub - perform process substitution</a></li>
<li class="right">
<div class="inline-search" role="search">
<form class="inline-search" action="../search.html" method="get">
<input placeholder="Quick search" type="text" name="q" />
<input type="submit" value="Go" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
</div>
</li>
<div id="old-docs-notice" style="display: none">
This documents an old version of fish.
<a href="../../current/">See the latest release.</a>
</div>
</ul>
</div>
<div class="document">
<div class="sphinxsidebar" role="navigation" aria-label="Main">
<div class="sphinxsidebarwrapper">
<div>
<h3><a href="../index.html">Documents</a></h3>
<ul class="current">
<li class="toctree-l1"><a class="reference internal" href="../index.html">Introduction</a></li>
<li class="toctree-l1"><a class="reference internal" href="../faq.html">Frequently asked questions</a></li>
<li class="toctree-l1"><a class="reference internal" href="../interactive.html">Interactive use</a></li>
<li class="toctree-l1"><a class="reference internal" href="../language.html">The fish language</a></li>
<li class="toctree-l1 current"><a class="reference internal" href="../commands.html">Commands</a></li>
<li class="toctree-l1"><a class="reference internal" href="../fish_for_bash_users.html">Fish for bash users</a></li>
<li class="toctree-l1"><a class="reference internal" href="../tutorial.html">Tutorial</a></li>
<li class="toctree-l1"><a class="reference internal" href="../completions.html">Writing your own completions</a></li>
<li class="toctree-l1"><a class="reference internal" href="../prompt.html">Writing your own prompt</a></li>
<li class="toctree-l1"><a class="reference internal" href="../design.html">Design</a></li>
<li class="toctree-l1"><a class="reference internal" href="../relnotes.html">Release notes</a></li>
<li class="toctree-l1"><a class="reference internal" href="../terminal-compatibility.html">Terminal Compatibility</a></li>
<li class="toctree-l1"><a class="reference internal" href="../contributing.html">Contributing To Fish</a></li>
<li class="toctree-l1"><a class="reference internal" href="../license.html">License</a></li>
</ul>
</div>
<search id="searchbox" style="display: none" role="search">
<h3 id="searchlabel">Quick search</h3>
<div class="searchformwrapper">
<form class="search" action="../search.html" method="get">
<input type="text" name="q" aria-labelledby="searchlabel" autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false"/>
<input type="submit" value="Go" />
</form>
</div>
</search>
<script>document.getElementById('searchbox').style.display = "block"</script>
<div>
<h4><a href="../index.html">Sections</a></h4>
<ul>
<li><a class="reference internal" href="#">psub - perform process substitution</a><ul>
<li><a class="reference internal" href="#synopsis">Synopsis</a></li>
<li><a class="reference internal" href="#description">Description</a></li>
<li><a class="reference internal" href="#example">Example</a></li>
</ul>
</li>
</ul>
</div>
</div>
</div>
<div class="documentwrapper">
<div class="bodywrapper">
<div class="body" role="main">
<section id="psub-perform-process-substitution">
<h1>psub - perform process substitution<a class="headerlink" href="#psub-perform-process-substitution" title="Link to this heading">¶</a></h1>
<section id="synopsis">
<h2>Synopsis<a class="headerlink" href="#synopsis" title="Link to this heading">¶</a></h2>
<div class="highlight-fish-synopsis notranslate"><div class="highlight"><pre><span></span><span class="nf">COMMAND1</span><span class="w"> </span><span class="g g-Other">(</span><span class="w"> </span><span class="no">COMMAND2</span><span class="w"> </span><span class="g g-Other">|</span><span class="w"> </span><span class="no">psub</span><span class="w"> </span><span class="g g-Other">[</span><span class="no">-F</span><span class="w"> </span><span class="g g-Other">|</span><span class="w"> </span><span class="no">--fifo</span><span class="g g-Other">]</span><span class="w"> </span><span class="g g-Other">[</span><span class="no">-f</span><span class="w"> </span><span class="g g-Other">|</span><span class="w"> </span><span class="no">--file</span><span class="g g-Other">]</span><span class="w"> </span><span class="g g-Other">[(</span><span class="no">-s</span><span class="w"> </span><span class="g g-Other">|</span><span class="w"> </span><span class="no">--suffix</span><span class="g g-Other">)</span><span class="w"> </span><span class="no">SUFFIX</span><span class="g g-Other">]</span><span class="w"> </span><span class="g g-Other">)</span>
</pre></div>
</div>
</section>
<section id="description">
<h2>Description<a class="headerlink" href="#description" title="Link to this heading">¶</a></h2>
<p>Some shells (e.g., ksh, bash) feature a syntax that is a mix between command substitution and piping, called process substitution. It is used to send the output of a command into the calling command, much like command substitution, but with the difference that the output is not sent through commandline arguments but through a named pipe, with the filename of the named pipe sent as an argument to the calling program. <code class="docutils literal notranslate"><span class="pre">psub</span></code> combined with a regular command substitution provides the same functionality.</p>
<p>The following options are available:</p>
<dl class="simple">
<dt><strong>-f</strong> or <strong>--file</strong></dt><dd><p>Use a regular file instead of a named pipe to communicate with the calling process. This will cause <code class="docutils literal notranslate"><span class="pre">psub</span></code> to be significantly slower when large amounts of data are involved, but has the advantage that the reading process can seek in the stream. This is the default.</p>
</dd>
<dt><strong>-F</strong> or <strong>--fifo</strong></dt><dd><p>Use a named pipe rather than a file. You should only use this if the command produces no more than 8 KiB of output. The limit on the amount of data a FIFO can buffer varies with the OS but is typically 8 KiB, 16 KiB or 64 KiB. If you use this option and the command on the left of the psub pipeline produces more output a deadlock is likely to occur.</p>
</dd>
<dt><strong>-s</strong> or <strong>--suffix</strong> <em>SUFFIX</em></dt><dd><p>Append SUFFIX to the filename.</p>
</dd>
<dt><strong>-h</strong> or <strong>--help</strong></dt><dd><p>Displays help about using this command.</p>
</dd>
</dl>
</section>
<section id="example">
<h2>Example<a class="headerlink" href="#example" title="Link to this heading">¶</a></h2>
<div class="highlight-fish-docs-samples notranslate"><div class="highlight"><pre><span></span><span class="nf">diff</span><span class="w"> </span><span class="o">(</span><span class="nf">sort</span><span class="w"> </span><span class="no">a.txt</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">psub</span><span class="o">)</span><span class="w"> </span><span class="o">(</span><span class="nf">sort</span><span class="w"> </span><span class="no">b.txt</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">psub</span><span class="o">)</span>
<span class="c"># shows the difference between the sorted versions of files ``a.txt`` and ``b.txt``.</span>
<span class="nf">source-highlight</span><span class="w"> </span><span class="no">-f</span><span class="w"> </span><span class="no">esc</span><span class="w"> </span><span class="o">(</span><span class="nf">cpp</span><span class="w"> </span><span class="no">main.c</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">psub</span><span class="w"> </span><span class="no">-f</span><span class="w"> </span><span class="no">-s</span><span class="w"> </span><span class="no">.c</span><span class="o">)</span>
<span class="c"># highlights ``main.c`` after preprocessing as a C source.</span>
</pre></div>
</div>
</section>
</section>
<div class="clearer"></div>
</div>
</div>
</div>
<div class="clearer"></div>
</div>
<div class="related" role="navigation" aria-label="Related">
<h3>Navigation</h3>
<ul>
<li><img src="../_static/fish.png" alt=""
style="width: 80px; height: 80px; vertical-align: middle; margin-top: -1px"/></li>
<li><a href="https://fishshell.com/">fish-shell</a> »</li>
<a href="../index.html">fish-shell 4.2.1 documentation</a> »
<li class="nav-item nav-item-1"><a href="../commands.html" >Commands</a> »</li>
<li class="nav-item nav-item-this"><a href="">psub - perform process substitution</a></li>
<li class="right">
<div class="inline-search" role="search">
<form class="inline-search" action="../search.html" method="get">
<input placeholder="Quick search" type="text" name="q" />
<input type="submit" value="Go" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
</div>
</li>
<div id="old-docs-notice" style="display: none">
This documents an old version of fish.
<a href="../../current/">See the latest release.</a>
</div>
</ul>
</div>
<div class="footer">
© Copyright fish-shell developers.
<br />
<a href="https://github.com/fish-shell/fish-shell/issues">Found a bug</a>?
<br />
Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 8.2.3.
</div>
</div>
<script type="text/javascript">
FISH_DOCS_VERSION = "4.2";
function copy_to_clipboard(it) {
// Find the pre tag we're interested in.
var pre = it.target;
while (pre.tagName != "PRE") pre = pre.parentNode;
var txt = "";
// Cheesy: If we have a prompt,
// we only copy prompted lines,
// by splitting and matching and stuff
if (pre.querySelector('span.gp')) {
var texts= [];
for (var line of pre.innerText.split('\n')) {
if (line.match(/^>_?.*/)) {
texts.push(line.replace(/^>_?/, ""));
}
}
txt = texts.join("\n");
} else {
// Even cheesier: If we don't have a prompt, we remove the button text from the end.
var txt = pre.innerText.substring(0, pre.innerText.length - it.target.innerText.length).trim();
}
navigator.clipboard.writeText(txt).then(function() {
// Success - set the text to indicate it,
// then set it back after 2 seconds.
var span = pre.querySelector("button span");
if (span) {
var oldText = span.innerText;
span.innerText = "COPIED!";
setTimeout(function() {
span.innerText = oldText;
}, 2000);
}
}, function() {
});
}
(function () {
// Add copy buttons to all the codeblocks.
var codeblocks = document.querySelectorAll('div > pre');
var button = document.createElement('button');
var span = document.createElement('span');
span.innerText = "COPY";
button.appendChild(span);
for (var i of codeblocks) {
var newButton = button.cloneNode(true);
newButton.addEventListener('click', copy_to_clipboard);
i.appendChild(newButton);
}
})();
</script>
</body>
</html>
|
