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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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sh(1)							      General Commands Manual							     sh(1)

NAME
sh - overview of various system shells SYNOPSIS
POSIX Shell option] ... string] [arg ...] option] ... string] [arg ...] Korn Shell option] ... string] [arg ...] option] ... string] [arg ...] C Shell [command_file] [argument_list ...] Key Shell DESCRIPTION
Remarks The POSIX .2 standard requires that, on a POSIX-compliant system, executing the command activates the POSIX shell (located in file on HP-UX systems), and executing the command produces an on-line manual entry that displays the syntax of the POSIX shell command-line. However, the command has historically been associated with the conventional Bourne shell, which could confuse some users. To meet stan- dards requirements and also clarify the relationships of the various shells and where they reside on the system, this entry provides com- mand-line syntax and a brief description of each shell, and lists the names of the manual entries where each shell is described in greater detail. The Bourne shell is removed from the system starting with HP-UX 11i Version 1.5. Please use the POSIX shell as an alternative. Shell Descriptions The HP-UX operating system supports the following shells: POSIX-conforming command programming language and command interpreter residing in file Can execute commands read from a terminal or a file. This shell conforms to current POSIX standards in effect at the time the HP-UX system release was introduced, and is similar to the Korn shell in many respects. Similar in many respects to the Korn shell, the POSIX shell contains a history mechanism, supports job control, and provides various other useful features. Korn-shell command programming language and commands interpreter residing in file Can execute commands read from a terminal or a file. This shell, like the POSIX shell, contains a his- tory mechanism, supports job control, and provides various other useful features. A command language interpreter that incorporates a command history buffer, C-language-like syntax, and job control facilities. Restricted version of the POSIX shell command interpreter. Sets up a login name and execution environment whose capabilities are more controlled (restricted) than normal user shells. restricted version of the Korn-shell command interpreter Sets up a login name and execution environment whose capabilities are more controlled (restricted) than normal user shells. An extension of the standard Korn Shell that uses hierarchical softkey menus and context-sensitive help. +--------------+--------------------+ | To obtain: | Use the command: | +--------------+--------------------+ | POSIX Shell | /usr/bin/sh ... | | Korn Shell | /usr/bin/ksh ... | | C Shell | /usr/bin/csh ... | | Key Shell | /usr/bin/keysh | +--------------+--------------------+ These shells can also be the default invocation, depending on the entry in the file. See also chsh(1). WARNINGS
Many manual entries contain descriptions of shell behavior or describe program or application behavior similar to ``the shell'' with a ref- erence to ``see sh(1)''. SEE ALSO
For more information on the various individual shells, see: keysh(1) Key Shell description. ksh(1) Korn Shell description. sh-posix(1) POSIX Shell description. csh(1) C Shell description. sh(1)
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