#include <pwd.h> int putpwent(const struct passwd *p, FILE *f);
The putpwent() function is the inverse of getpwent(). See getpwnam(3C). Given a pointer to a passwd structure created by getpwent(), getpwuid(), or getpwnam(), putpwent () writes a line on the stream f that matches the format of /etc/passwd.
The putpwent() function returns a non-zero value if an error was detected during its operation. Otherwise, it returns 0.
The putpwent() function is of limited utility, since most password files are maintained as Network Information Service (NIS) files that cannot be updated with this function. For this reason, the use of this function is discouraged. If used at all, it should be used with putspent(3C) to update the shadow file.
See attributes(5) for descriptions of the following attributes: