nlist(3elf)

nlist, nlist32, nlist64 -- get entries from name list

Synopsis

   cc [flag . . . ] file . . . -lelf [library] . . .
   
   #include <nlist.h>
   

   int nlist (const char file, struct nlist nl);
   int nlist32 (const char *file, struct nlist *);
   int nlist64 (const char *file, struct nlist64 *);

Description

nlist examines the name list in the executable file whose name is pointed to by file, and selectively extracts a list of values and puts them in the array of nlist structures pointed to by nl. The name list nl consists of an array of structures containing names of variables, types, and values. The list is terminated with a null name, that is, a null string is in the name position of the structure. Each variable name is looked up in the name list of the file. If the name is found, the type, value, storage class, and section number of the name are inserted in the other fields. The type field may be set to 0 if the file was not compiled with the -g option to cc(1). nlist will always return the information for an external symbol of a given name if the name exists in the file. If an external symbol does not exist, and there is more than one symbol with the specified name in the file (such as static symbols defined in separate files), the values returned will be for the last occurrence of that name in the file. If the name is not found, all fields in the structure except n_name are set to 0.

nlist and nlist32 are used with 32-bit ELF objects. nlist64 is used with 64-bit ELF objects.

If you want to examine symbols in a running kernel (and these symbols are associated with a dynamically loaded module), then you must use ioctl [see kmem(7)] or getksym(2), instead of nlist. To learn if a module is dynamically loaded, check to see if it is present in /etc/conf/mod.d.

Return values

All value entries are set to 0 if the file cannot be read or if it does not contain a valid name list.

nlist returns 0 on success, -1 on error.

References

a.out(4), Intro(3elf), getksym(2), kmem(7)