part of shnell – a source to source compiler enhancement tool
© Jens Gustedt, 2018
Evaluate the argument list as the names of environment variables
and substitue with the value
Usage:
Replace meta-variable NAMEx (${NAME0}, ${NAME1} …) by the values of environment variables VARIABLEx.
If NAMEx= is omitted NAMEx defaults to VARIABLEx.
Depending on the status of VARIABLEx, DEFAULTx can be used to control the returned value. The syntax is borrowed from the shell for parameter expansion. Therefore DEFAULTx must start with one of the characters -, + or ?, but other than for the shell = is not allowed:
-VALUEx sets VALUEx as default value if the environment variable is unset or empty.
+VALUEx provides an alternate value VALUEx, but only if the environment variable is set and not empty. Otherwise the result is empty.
?VALUEx is similar to the previous, but if the environment variable is unset or empty, the compilation is aborted.
Effect on the code that depends on this directive
All occurrences of ${NAMEx} etc (with the dollar and the braces) in the submitted text are replaced by the obtained value. All occurences of #${NAME0} (with the hash, the dollar and the braces) are replaced by the value put inside a C string.
Example:
#pragma CMOD amend env SH=SHELL PATH HOME:?1 ANS=ANSWER:-42
char shell[] = #${SH};
char path[] = #${PATH};
int const hasHome = ${HOME};
int const everything = ${ANS};This should usually be replaced by something similar to
char shell[] = "/bin/bash";
char path[] = "/usr/bin:/bin";
int const hasHome = 1;
int const everything = 42;unless the environment variable ANSWER is set to some different value (that value is then used for everything), or unless the environment variable HOME is unset or empty (the compilation would abort).
Coding and configuration
The following code is needed to enable the sh-module framework.SRC="$_" . "${0%%/${0##*/}}/import.sh"Imports
The following sh-modules are imported: