---
name: "strvars"
section: "3pub"
platform: "linux"
package: "publib-dev"
version: "0.40-4"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/strvars"
---

# strvars(3pub)

expand variables in string

## 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 occurred (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>\n", res);
```

## SEE ALSO

publib(3), [getenv(3)](/getenv/3.md)

## AUTHOR

Lars Wirzenius (lars.wirzenius@helsinki.fi)