如何在bash shell中的部分中打印passwd的最后一行

Question

I am very new to bash shell scripting and I have an assignment that wants me to read the last line of a copy of my linux installations (that is in the admin folder) passwd file which contains the user name, real name, home directory and login shell. I have tried the read command but it continues to output the entire file rather than just the last line and even so I need to be able to output in in sections, for example: echo $Username would output Admin or echo $Realname wold ouptut the users real name. I have also tried sed but I get a "cant read, no such file or directory error"

Edit: After receiving an email from my professor, I DO have to use the read command to get the information from the passwd file. However your responses have proved useful in helping me understand what I am doing so far. Thank you!

Here is a link to my list of objectives in this script

and here is the code that I have written that returns the entire passwd file:

file="/home/Admin/passwd"

while read -r f1 f2 f3 f4 f5 f6 f7
do
        echo "Username: $f1, Realname: $f2, Homedir: $f3, loginshell: $f4 "
done < "$file"

any help would be greatly appreciated, somehow I feel like I'm reading too much into the instructions but I would like some other opinions, thank you!

Answer 1

Welcome to the wonderful world of scripting!

Assignment does not seem to mention to use 'read' command, so, not giving out the solution completely, I would suggest you use redirection methods (try a Google search on Unix redirection, it is quite fun!)

I would also suggest searching on standard and error redirection in Unix. There are some nifty shortcuts quite easy to find.

Hope this helps!

Answer 2

you need use IFS to define the field separator, then understand what column is home directory, and login shell.

Understanding fields in /etc/passwd ( http://www.cyberciti.biz/faq/understanding-etcpasswd-file-format/ )

Here is the fix:

file="/home/Admin/passwd"

while IFS=: read -r f1 f2 f3 f4 f5 f6 f7
do
   echo "Username: $f1, Realname: $f5, Homedir: $f6, loginshell: $f7 "
done  < "$file"