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A function to massage a list of filenames to protect weirdo characters e.

It can be used for prototyping GUI applications. It has many additional features to make interactive use more convenient. The original Bourne shell isrc no built-in arithmetic operators.

Arrays must vasics declared before use, e,g. No ip translation, just echo the whole line In ksh and most newer versions of sh, “[” is replaced with a compatible internal command, but the argument parsing is performed as if it were an external command.

Unix shell scripting with ksh/bash

Wrap programs over which you have no control inside an environment that you can control. Save a copy of original stdout There is no return from an exec.


Functions may generate output to stdout, stderr, or any other file or filehandle. This could be used to configure a screen saver, for example. Standards committees worked over the Bourne shell and added many features of the Korn shell ksh88 and C shell to define a standard set of features which all compliant shells must have. Just echo the address we tried to look up Kill the command if it hasn’t finished when the timeout expires.

The book by Randal Michael contains 12 example ways to read a file line by line, which vary tremendously in efficiency. It is faster to run a single process than to run a separate lookup for each user. If any of the commands really care about inheriting open file Convert a decimal IP to hostname – calls ‘host’ each time If you follow textbooks on Bourne shell programming, all of the advice should apply no matter which of the Bourne-derived shells you use.

It will also have variable 7: The reserved word integer is an alias for typeset -i. Think of it as only one way for everything to work, but many possible ways to fail. When used inside a function, a local variable is created.

Remove the named variables. If we have not redirected standard output, save a copy of 4: Unfortunately, many vendors have added features over the years and achieving complete portability can be a challenge. Shell aliases apply only to the current shell. Since “find” may result in a very large list of pathnames, using the results directly may overflow command line buffers.


Run a subshell, with 4 duplicated to 1 so we get it in stdout. Function will return here – if backgrounded, the subprocess will exit.

The until form just negates the test. This is used for diagnostics when a variable should have grpup set and there is no sensible default value to use.

Download a compressed tar file of all example scripts used in these notes. If you do have permission to overwrite it, you will delete the previous contents. The patterns can be simple fixed text, or very complex regular expressions.

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Variables are black Not obvious if you have not seen this one before. MailPkg displaytext Tar, compress, split and uuendcode a set of files for mailing. If you don’t do this, the variable is local to this shell instance. A flexible editor which operates by applying editing rules to every line in a data stream in turn.

All file descriptors are closed when a script exits. Variables are treated as text strings, unless the context implies a numeric interpretation.

Fails on old Bourne shells. Many things in common with the Bourne shell, but many enhancements to improve interactive use.