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Operating Systems Linux UNIX Utility Development Conventions? Post 303040894 by wisecracker on Friday 8th of November 2019 09:27:41 AM
Old 11-08-2019
Hi MonilGome...

I will add to vbe's post and say if you want any of your code, whether it be a shell script, a dedicated compiled executable or a separately interpreted script, to be portable then make sure it is POSIX compliant; also if it is a dedicated executable and you intend it to be used as along with other utilities make sure you include a piping facility.
For example: echo "3 + 7" | bc ...
Also 'zsh', along with 'ksh[93]', has floating point arithmetic; DO NOT take this for granted, POSIX compliant shells only have integer arithmetic ONLY - so beware.

As a hobbyist coder, this is just my 5 pennoth...

Bazza...
 

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shells(4)							   File Formats 							 shells(4)

NAME
shells - shell database SYNOPSIS
/etc/shells DESCRIPTION
The shells file contains a list of the shells on the system. Applications use this file to determine whether a shell is valid. See getuser- shell(3C). For each shell a single line should be present, consisting of the shell's path, relative to root. A hash mark (#) indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted by the routines which search the file. Blank lines are also ignored. The following default shells are used by utilities: /bin/bash, /bin/csh, /bin/jsh, /bin/ksh, /bin/ksh93, /bin/pfcsh, /bin/pfksh, /bin/pfsh, /bin/sh, /bin/tcsh, /bin/zsh, /sbin/jsh, /sbin/sh, /usr/bin/bash, /usr/bin/csh, /usr/bin/jsh, /usr/bin/ksh, /usr/bin/ksh93, /usr/bin/pfcsh, /usr/bin/pfksh, /usr/bin/pfsh, and /usr/bin/sh, /usr/bin/tcsh, /usr/bin/zsh, and /usr/sfw/bin/zsh. /etc/shells overrides the default list. Invalid shells in /etc/shells could cause unexpected behavior, such as being unable to log in by way of ftp(1). FILES
/etc/shells list of shells on system SEE ALSO
vipw(1B), ftpd(1M), sendmail(1M), getusershell(3C), aliases(4) SunOS 5.11 20 Nov 2007 shells(4)
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