Adding a user in linux using C

[ankushpandit]

Hi all,


I am a newbie in area of programming applications for Linux using C. The application I am trying to build need to take following inputs from the user.

1) username
2) password

This application then need to add the user to linux. I need to do this using C code. I have tried the following thing but it didnt work.

Using system("adduser user1"); and system("passwd user1") . This does works, the user is added to the system. But the problem here is that the program waits for an input from user when passwd is executed. The program I am building should not wait for user input as the user has already entered the username and password before execution of these system calls as these should be added on to a file.

May be this whole approach to the problem is wrong. Using the above method I am able to add a user but could not set the password. Another thing that I found out was the -p switch in adduser command. Which needs a crypted passwd. For some reason I am not able to add crypt() to my code. Other wise the next thing I would have done was

system("adduser user1 -p XXXXXX")

where XXXXXX was a cryped passwd.

Please help any examples or webpages or code is welcome.

Is there another way of doing this. Coz I know making system calls to add users and password does not sounds like good programming.


Ankush Pandit

PS - This application will be running as "root".

[GNU-Fan]

Well, the useradd program is to be found on virtually any GNU/Linux system.
Just get the source code and study it.

[coopstah13]

man crypt

in order to use crypt function call, you need to include unistd.h

[Rubberman]

You can open a pipe in your program, dup2() that to your stdin file stream, write the password data to the pipe, and then fork/exec to the adduser program and it will read from the pipe to take the appropriate data. Non-intuitive, I know, but it does work. See if you can work it out. If not, I'll provide some more "hints".