check new user with /etc/passwd

[Lim Boon Jye]

example

# useradd hello 

how to i suppose to do if hello is existed in passwd file?

the error will come out

user hello exist

so my question is if i do like

# Enter username: 
read username

//concept
if [ $username existed ]
then
     echo " error"
else
     ...
     ...
fi

i don't know how to code it. can someone teach?

[kbw]

You need getpwnam()
http://pubs.opengroup.org/onlinepubs/007908799/xsh/getpwnam.html

[keskiverto]

He would, if he were using C/C++/etc. However, according to his threads on this topic, his homework is to write a shell script. Luckily, there are simple programs that do call getpwnam() and have exit status to test.

There must be Fora out there focused on basic shell scripting and less focused on the use of C++ to interact with UNIX-like system.