Questions on bash

[Cixy]

Met some problems on bash programing:
1. how to read a line from file and save it into a variable?
2. how to reserve a string?
3. does reg exp support number caculation? how?
4. how to return value in a function and how to retrieve it outside function?
5. how to format the output string?

Thanks for your reply!

[mahongxi]

1.
$line_str=$(sed "2 p" -n t.txt) 2 is line number

[Cixy]

Thanks pacman and mahongxi,

pacman,
I tried your code, but only the first line was successfully read.
In fact in question 1, I want to write an iterator to go through the whole file line by line.
In question 2, I want to reverse a string (sorry for my typo :P)

mahongxi
In your method, how to count the number of lines in a file?

Thanks again and appreciate for you reply.

[pacman2000]

1. read a < t.txt
2. ???
3. i=`expr $1 + 1` ?
4. man bash , see FUNCTIONS
5. printf

[Cixy]

man awk... too many to read... I have to say my english is not good(use english just because no chinese ime installed on the lab pc)

so... could you please give a clear answer for my questions?

Thanks,

[gettext]

用awk更合适。man awk

[Cixy]

唉，还是去UNIX站点寻求帮助吧，谢谢两位了