elf_getscn(3E)

DESCRIPTION

These functions provide indexed and sequential access to the sections associated with the ELF descriptor elf. If the program is building a new file, it is responsible for creating the file's ELF header before creating sections; see elf_getehdr(3E).

elf_getscn returns a section descriptor, given an index into the file's section header table. Note the first ``real'' section has index 1. Although a program can get a section descriptor for the section whose index is 0 (SHN_UNDEF, the undefined section), the section has no data and the section header is ``empty'' (though present). If the specified section does not exist, an error occurs, or elf is null, elf_getscn returns a null pointer.

elf_newscn creates a new section and appends it to the list for elf. Because the SHN_UNDEF section is required and not ``interesting'' to applications, the library creates it automatically. Thus the first call to elf_newscn for an ELF descriptor with no existing sections returns a descriptor for section 1. If an error occurs or elf is null, elf_newscn returns a null pointer.

After creating a new section descriptor, the program can use elf_getshdr to retrieve the newly created, ``clean'' section header. The new section descriptor will have no associated data (see elf_getdata(3E)). When creating a new section in this way, the library updates the e_shnum member of the ELF header and sets the ELF_F_DIRTY bit for the section (see elf_flag(3E)). If the program is building a new file, it is responsible for creating the file's ELF header (see elf_getehdr(3E)) before creating new sections.

elf_nextscn takes an existing section descriptor, scn, and returns a section descriptor for the next higher section. One may use a null scn to obtain a section descriptor for the section whose index is 1 (skipping the section whose index is SHN_UNDEF). If no further sections are present or an error occurs, elf_nextscn returns a null pointer.

elf_ndxscn takes an existing section descriptor, scn, and returns its section table index. If scn is null or an error occurs, elf_ndxscn returns SHN_UNDEF.

EXAMPLES

An example of sequential access appears below. Each pass through the loop processes the next section in the file; the loop terminates when all sections have been processed.

SEE ALSO

elf(3E), elf_begin(3E), elf_flag(3E), elf_getdata(3E), elf_getehdr(3E), elf_getshdr(3E).