These functions are glibc-specific.
An argz vector is a pointer to a character buffer together with a length. The intended interpretation of the character buffer is array of strings, where the strings are separated by NUL bytes. If the length is nonzero, the last byte of the buffer must be a NUL.
These functions are for handling argz vectors. The pair (NULL,0) is an argz vector, and, conversely, argz vectors of length 0 must have NULL pointer. Allocation of nonempty argz vectors is done using malloc(3), so that free(3) can be used to dispose of them again.
argz_add() adds the string str at the end of the array *argz, and updates *argz and *argz_len.
argz_add_sep() is similar, but splits the string str into substrings separated by the delimiter delim. For example, one might use this on a Unix search path with delimiter :.
argz_append() appends the argz vector (buf,buf_len) after (*argz,*argz_len) and updates *argz and *argz_len. (Thus, *argz_len will be increased by buf_len.)
argz_count() counts the number of strings, that is, the number of NUL bytes, in (argz,argz_len).
argz_create() converts a Unix-style argument vector argv, terminated by (char *) 0, into an argz vector (*argz,*argz_len).
argz_create_sep() converts the NUL-terminated string str into an argz vector (*argz,*argz_len) by breaking it up at every occurrence of the separator sep.
argz_delete() removes the substring pointed to by entry from the argz vector (*argz,*argz_len) and updates *argz and *argz_len.
argz_extract() is the opposite of argz_create(). It takes the argz vector (argz,argz_len) and fills the array starting at argv with pointers to the substrings, and a final NULL, making a Unix-style argv vector. The array argv must have room for argz_count(argz,argz_len") + 1" pointers.
argz_insert() is the opposite of argz_delete(). It inserts the argument entry at position before into the argz vector (*argz,*argz_len) and updates *argz and *argz_len. If before is NULL, then entry will inserted at the end.
argz_next() is a function to step trough the argz vector. If entry is NULL, the first entry is returned. Otherwise, the entry following is returned. It returns NULL if there is no following entry.
argz_replace() replaces each occurrence of str with with, reallocating argz as necessary. If replace_count is non-NULL, *replace_count will be incremented by the number of replacements.
argz_stringify() is the opposite of argz_create_sep(). It transforms the argz vector into a normal string by replacing all NULs except the last by sep.
All argz functions that do memory allocation have a return type of error_t, and return 0 for success, and ENOMEM if an allocation error occurs.
Argz vectors without final NUL may lead to Segmentation Faults.
These functions are a GNU extension. Handle with care.