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\read
Synopsis:
\readnumber tomacro
Make the command macro contain the next line of input from text
stream number, as in \read5 to\data
.
This opens the file email.tex for reading, puts the contents of
the first line into the command \email
, and then closes the file.
\newread\recipientfile \openin\recipientfile=email \read\file to\email \typeout{Email address: \email} \closein\recipientfile
If number is outside the range from 0 to 15 or if no file of
that number is open, or if the file has ended, then \read
will
take input from the terminal. Note, though, that the natural way in
LaTeX to take input from the terminal is \typein
(see \typein).
To read in an entire file at once use \input
(see \input) or
\include
(see \include & \includeonly).
A common reason to want to read from a data file is to do mail merge. CTAN has a number of packages for that; one is datatool.