The following routines provide the ability to access and update
awk-level variables by name. In compiler terminology,
identifiers of different kinds are termed symbols, thus the “sym”
in the routines’ names. The data structure that stores information
about symbols is termed a symbol table.
The functions are as follows:
awk_bool_t sym_lookup(const char *name,
Fill in the
awk_value_t structure pointed to by
with the value of the variable named by the string
name, which is
a regular C string.
wanted indicates the type of value expected.
Return true if the actual type matches
wanted, and false otherwise.
In the latter case,
result->val_type indicates the actual type
(see Table 16.1).
awk_bool_t sym_update(const char *name, awk_value_t *value);
Update the variable named by the string
name, which is a regular
C string. The variable is added to
gawk’s symbol table
if it is not there. Return true if everything worked, and false otherwise.
Changing types (scalar to array or vice versa) of an existing variable
is not allowed, nor may this routine be used to update an array.
This routine cannot be used to update any of the predefined
variables (such as
An extension can look up the value of
gawk’s special variables.
However, with the exception of the
PROCINFO array, an extension
cannot change any of those variables.
CAUTION: It is possible for the lookup of
PROCINFOto fail. This happens if the
awkprogram being run does not reference
PROCINFO; in this case,
gawkdoesn’t bother to create the array and populate it.