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:

#!/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.

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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.

<~~lang~~ ~~bash~~>f() {

<syntaxhighlight lang="sh">f() {

cat <<!

here $1

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expr "`f string`"

# 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.

<~~lang~~ ~~bash~~>f() {

<syntaxhighlight lang="sh">f() {

cat <<!

here $1

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var=`f string`

expr "$var"

# Output: here string</~~lang~~>

# Output: here string</syntaxhighlight>