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Top Forums UNIX for Dummies Questions & Answers how to expand environment variables in a file? Post 302330569 by jim mcnamara on Wednesday 1st of July 2009 04:29:14 PM
Old 07-01-2009
I think you mean to 'get the value of' a variable or maybe dereference it.

Do you mean you want to create a file using a variable as a filename?
Code:
SourceFilePath=/db1/Src/test 
var=${SourceFilePath}/file.txt
> $var     # this creates an empty file named /db1/Src/test/file.txt

 

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STRVARS(3pub)						       C Programmer's Manual						     STRVARS(3pub)

NAME
strvars - expand variables in string SYNOPSIS
#include <publib.h> int strvars(char **res, const char *str, char *(*expand)(const char *)); DESCRIPTION
strvars will replaces references to variables in the string str with the values of the variables. A reference to a variable is of the form $(foo) or $x (where x is a single character, but not $). A dollar sign is expressed in the string as $$, and will be converted to $ in the output. Memory for the expanded string is allocated dynamically, and *res is set to point to it. The values of the variables are fetched using the function expand. It is given the name of the variable as its argument, and must return a pointer to the value, or NULL if that variable doesn't exist. RETURN VALUE
strvars will return 0 if successful, or NULL if an error occured (malformed input string, result too big, or unknown variable). EXAMPLE
To replace references to environment variables, one would the following. #include <publib.h> #include <stdlib.h> char line[1024]; char *res; if (strvars(&res, line, getenv) == NULL) errormsg(1, 0, "strvars failed"); printf("res = <%s> ", res); SEE ALSO
publib(3), getenv(3) AUTHOR
Lars Wirzenius (lars.wirzenius@helsinki.fi) Publib C Programmer's Manual STRVARS(3pub)
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