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    <p>A shell variable is just a piece of memory inside the running shell process. An Environment Variable is a variable that the shell copies into its <em>environment</em> prior to calling another program.</p> <p>To understand the limitations of Environment Variables, one must understand the concept of the <em>environment</em> of a process: It's a single section of memory that is not <em>shared</em> between processes, but <em>passed on</em> from one process to another during an <a href="http://www.kernel.org/doc/man-pages/online/pages/man3/exec.3.html" rel="nofollow noreferrer"><code>exec</code></a> system call. (See also: <a href="https://unix.stackexchange.com/questions/17758/exception-of-inheritance-of-environment-variables">Environment Variables</a>)</p> <p>The environment gets passed on from one process to the next, and subsequent processes can change it prior to calling another program.</p> <p>This environment also has certain restrictions: It can consist only of a list of nul-terminated strings, terminated by a null-pointer. Essentially, it's an array of strings.</p> <p>Note that these strings do not need to follow the <code>VARNAME=value</code> structure, which is a convention adopted by early unix shells.</p> <p><code>ksh93</code> does support shell <em>co-processes</em>, though.</p> <p>After starting a child process, the parent can connect to the child's stdin and stdout with the <code>&lt;&amp; p</code> and <code>&gt;&amp; p</code> redirection operators. It can be a challenge to handle these correctly, as many operations close their stdout on termination, which will close the pipe to the child.</p>
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    1. POPass variable from a child to parent in KSH
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    1. USHenk Langeveld
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    1. COThanks for helping, btw i know what is an environment and i know how variables scopes works. Maybe its gonna help someone else ... Keep thinking trap stdin/stdout may be dangerous because of syntax error catching ... i prefer use Guru's solution because its safer than this one.
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      1. USXavier S.
    2. COGuru's solution is safe and simple. I just wanted to make sure that it's more than just scope - it's a different address space, and the data only flows one way. As IPC goes, it's a pipe or a file for shells. And with ksh93, a socket might just work as well.
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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