how to update file in unix ?

Edit it.

Add your contents and save. (?) is one way of doing it.

You want to update a file means what you exactly want.

Do you want to change the timestamp of the file or contents from the file ?
if contents then obviously us vi editor and make changes.
if you want to change timestamp then use touch command.
check man touch for the same.

i want to change the content of file .
i know vi editor but which command is for update file.

i want to update my content in file.
like account holder deposite may be increase or discrease what i do?

Sorry, but your question still seems a little open ended. Lets start with identifiying some of the details of your problem:

1) Is your file a binary file, or ASCII file?
2) What identifies a particular account or entry? e.g. account number
3) What is the record structure for an account or entry?

In general terms you may want to consider using the sed or awk command. Read the contents of your file from standard input. The sed or awk commands will allow you to subsitute some of the input stream as you send it to standard output.

Why don't you give us a bit of background...on your job and what you are trying to do...

It would help greatly to understand where you are coming from.




To edit a file simply open it with vi... then edit it and :wq! to save it thereby updating it.