Script portability

Make GRASS shell scripts portable

Portable shell scripting is something of a black art, since with the evolution and derivation of the UNIX shell, the definition of "portable" is perhaps ambiguous.

_Simon__Nattrass_

Guidelines

Conditionals

Conditional with [ ... ] should replaced by __test__

               	         
if [ -f foo.c ] 
then
...
fi

as here:

 
if test -f foo.c
then
...
fi

Arithmetics

Expression with $(( ... ))

 
x=$(($x+1))

are more portable if using __expr__

              
x=`expr $x + 1`

The $(command) expression versus `command`

The $(command) may be supported in many modern Bourne shells but for pure Bourne shells use of `command` is favored, although this method tends to lead to confusion when the backquotes contain the characters $, ` and \. In such cases remember to use the character \ to escape these sequences.

References

• Making Scripts Portable by Simon Nattrass
• GRASS and Shell