172 lines
4.7 KiB
HTML
172 lines
4.7 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>About Shell Scripts</title>
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Begin Header Records ========================================== -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<a name="Top_Of_Page"></a>
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<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
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</script>
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<h2>About Shell Scripts</h2>
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<p>A <strong>shell</strong> (or shell interpreter) is a command interpreter.
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The shell interprets text strings and performs some function for each string.
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As part of interpreting the string, the shell may do variable or wildcard
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replacement or change the string in some way. Typically, the shell itself
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performs functions specified by internal commands and spawns a child process to
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perform processing on the external commands. Depending on the command, the
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shell then does one of the following:</p>
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<ul>
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<li>Waits for the child process to complete</li>
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<li>Continues processing with the next command</li>
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</ul>
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<p>A <strong>shell script</strong> is a text file whose format defines the
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following:</p>
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<ul>
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<li>A shell interpreter (path and program)</li>
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<li>Options or arguments to pass to the shell</li>
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<li>Text to be interpreted as a series of commands to the shell</li>
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</ul>
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<p>The format of a shell script, starting on line one and column one, is as
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follows:</p>
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<pre>
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#!interpreter_path <options>
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text to be interpreted
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text to be interpreted
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.
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.
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.
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</pre>
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<p>where</p>
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<dl>
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<dd>
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<p><samp>interpreter_path</samp> is the shell interpreter.</p>
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</dd>
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<dd>
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<p><samp>options</samp> are the options to pass to the shell interpreter.</p>
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</dd>
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</dl>
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<p>The <strong>spawn()</strong> and <strong>spawnp()</strong> functions support
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shell scripts. i5/OS currently provides the Qshell Interpreter. The Qshell
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Interpreter is a standard command interpreter for i5/OS based on the POSIX
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1003.2 standard and X/Open CAE Specification for Shell and Utilities.</p>
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<p><strong>Examples</strong></p>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<p>The following is an example of using <strong>spawn()</strong> to run a shell
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script written for the Qshell Interpreter:</p>
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<pre>
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#include <stdio.h>
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#include <spawn.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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int main(int argc, char *argv[])
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{
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int fd_map[3], stdoutFds[2];
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char *xmp_argv[4], *xmp_envp[3];
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struct inheritance xmp_inherit = {0};
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char buffer[20];
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pid_t child_pid, wait_rv;
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int wait_stat_loc, rc;
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xmp_argv[0] = "/home/myuserid/myscript";
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xmp_argv[1] = "Hello";
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xmp_argv[2] = "world!";
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xmp_argv[3] = NULL;
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xmp_envp[0] =
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"NLSPATH=/QIBM/ProdData/OS400/Shell/MRI2924/%N";
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xmp_envp[1] = "QIBM_USE_DESCRIPTOR_STDIO=Y";
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xmp_envp[2] = NULL;
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if (pipe(stdoutFds) != 0) {
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printf("failure on pipe\n");
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return 1;
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}
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fd_map[0] = stdoutFds[1];
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fd_map[1] = stdoutFds[1];
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fd_map[2] = stdoutFds[1];
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if ((child_pid = spawn("/home/myuserid/myscript", 3,
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fd_map, &xmp_inherit, xmp_argv,
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xmp_envp)) == -1) {
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printf("failure on spawn\n");
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return 1;
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}
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if ((wait_rv = waitpid(child_pid,
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&wait_stat_loc, 0)) == -1) {
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printf("failure on waitpid\n");
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return 1;
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}
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close(stdoutFds[1]);
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while ((rc = read(stdoutFds[0],
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buffer, sizeof(buffer))) > 0) {
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buffer[rc] = '\0';
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printf("%s", buffer);
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}
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close(stdoutFds[0]);
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return 0;
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}
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</pre>
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<p>where "/home/myuserid/myscript" could look like the following:</p>
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<pre>
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#!/usr/bin/qsh
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print $1 $2
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</pre>
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<strong>Example Output:</strong>
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<pre>
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Hello world!
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</pre>
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<br>
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2" width="600">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"unix11.htm">Process-Related APIs</a> | <a href="aplist.htm">APIs by
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category</a> </td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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