Bourne Shell: Difference between revisions

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A Bourne Shell script begins with a [[wp:shebang (Unix)|shebang]] (also known as a ''hashbang'') like this, which tells the operating system to use the Bourne compatible shell interpreter:
A Bourne Shell script begins with a [[wp:shebang (Unix)|shebang]] (also known as a ''hashbang'') like this, which tells the operating system to use the Bourne compatible shell interpreter:


<syntaxhighlight lang="sh">
#!/bin/sh
#!/bin/sh
</syntaxhighlight>


In 2009, ''[[wp:Computerworld|Computerworld]]'' published an in-depth interview with Steve Bourne, "[https://web.archive.org/web/20100212210742/computerworld.com.au/article/279011/a-z_programming_languages_bourne_shell_sh/ The A-Z of Programming Languages: Bourne shell, or sh]", which details the Bourne shell origins and design decisions.
In 2009, ''[[wp:Computerworld|Computerworld]]'' published an in-depth interview with Steve Bourne, "[https://web.archive.org/web/20100212210742/computerworld.com.au/article/279011/a-z_programming_languages_bourne_shell_sh/ The A-Z of Programming Languages: Bourne shell, or sh]", which details the Bourne shell origins and design decisions.
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Bourne Shell and Heirloom Shell have problems with here documents. Here is one such problem. A substitution, inside a here document, inside backquotes, inside double quotes, does insert too many backslashes.
Bourne Shell and Heirloom Shell have problems with here documents. Here is one such problem. A substitution, inside a here document, inside backquotes, inside double quotes, does insert too many backslashes.


<lang bash>f() {
<syntaxhighlight lang="sh">f() {
cat <<!
cat <<!
here $1
here $1
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expr "`f string`"
expr "`f string`"
# Output from Bourne Shell: here \s\t\r\i\n\g
# Output from Bourne Shell: here \s\t\r\i\n\g
# Correct output: here string</lang>
# Correct output: here string</syntaxhighlight>


The workaround is to move the backquotes to an assignment.
The workaround is to move the backquotes to an assignment.


<lang bash>f() {
<syntaxhighlight lang="sh">f() {
cat <<!
cat <<!
here $1
here $1
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var=`f string`
var=`f string`
expr "$var"
expr "$var"
# Output: here string</lang>
# Output: here string</syntaxhighlight>

Latest revision as of 12:35, 5 July 2023

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Bourne Shell is an implementation of UNIX Shell. Other implementations of UNIX Shell.

The Bourne Shell is a Unix shell upon which many shells are based; notably the Korn shell and Bourne Again SHell. (The other major tree of Unix shells descend from csh.)

Portable Shell Syntax is the scripting language syntax used by the System V Bourne shell. This syntax is compatible with the heirloom shell and is the syntax documented in most Unix books. Examples marked "Works with: Bourne Shell" should work in any of the Bourne-compatible shells.

A Bourne Shell script begins with a shebang (also known as a hashbang) like this, which tells the operating system to use the Bourne compatible shell interpreter:

#!/bin/sh

In 2009, Computerworld published an in-depth interview with Steve Bourne, "The A-Z of Programming Languages: Bourne shell, or sh", which details the Bourne shell origins and design decisions.

Bugs

Bourne Shell and Heirloom Shell have problems with here documents. Here is one such problem. A substitution, inside a here document, inside backquotes, inside double quotes, does insert too many backslashes.

f() {
	cat <<!
here $1
!
}

expr "`f string`"
# Output from Bourne Shell:     here \s\t\r\i\n\g
# Correct output:               here string

The workaround is to move the backquotes to an assignment.

f() {
	cat <<!
here $1
!
}

var=`f string`
expr "$var"
# Output:     here string