Bash read
Internal
Overview
read [-p prompt] name name2 ...
Read a line from the stdin or from the file descriptor specified with -u, and assign the first word to the variable associated with the first name, the second to the variable associated with the second name, and so on, with the leftover words and their intervening separators assigned to the variable associated with the last name. If there are fewer words than variable names, the variables associated with the remaining names are assigned empty values.
The words are split using the IFS characters. The backslash character (\) may be used to remove any special meaning for the next character read and for line continuation.
If -p prompt option is used, read displays the specified prompt on standard error, without a trailing new-line, before attempting to read any input. The prompt is displayed only if input is coming from a terminal.
Timeout
Fixed Number of Characters
-n nchars
If -n option is used read returns after reading nchars characters rather than waiting for a complete line of input.
Array Assignment
-a aname
If -a option is used, he words are assigned to sequential indices of the array variable aname, starting at 0. aname is unset before any new values are assigned. Other name arguments are ignored.
-r Backslash does not act as an escape character. The back-
slash is considered to be part of the line. In particu-
lar, a backslash-newline pair may not be used as a line
continuation.
-s Silent mode. If input is coming from a terminal, charac-
ters are not echoed.
-t timeout
Cause read to time out and return failure if a complete
line of input is not read within timeout seconds. This
option has no effect if read is not reading input from
the terminal or a pipe.
-u fd Read input from file descriptor fd.
If no names are supplied, the line read is assigned to the vari-
able REPLY. The return code is zero, unless end-of-file is
encountered, read times out, or an invalid file descriptor is
supplied as the argument to -u.