4.31. How do I export or pass variables back into the environment?
4.31.1. - on Unix platforms
Suppose that line #1, word #2 of the file 'terminals' contains a
value to be put in your TERM environment variable. Sed cannot
export variables directly to the shell, but it can pass strings to
shell commands. To set a variable in the Bourne shell:
TERM=`sed 's/^[^ ][^ ]* \([^ ][^ ]*\).*/\1/;q' terminals`;
export TERM
If the second word were "Wyse50", this would send the shell command
"TERM=Wyse50".
4.31.2. - on MS-DOS or 4DOS platforms
Sed cannot directly manipulate the environment. Under DOS, only
batch files (.BAT) can do this, using the SET instruction, since
they are run directly by the command shell. Under 4DOS, special
4DOS commands (such as ESET) can also alter the environment.
Under DOS or 4DOS, sed can select a word and pass it to the SET
command. Suppose you want the 1st word of the 2nd line of MY.DAT
put into an environment variable named %PHONE%. You might do this:
@echo off
sed -n "2 s/^\([^ ][^ ]*\) .*/SET PHONE=\1/p;3q" MY.DAT > GO_.BAT
call GO_.BAT
echo The environment variable for PHONE is %PHONE%
:: cleanup
del GO_.BAT
The sed script assumes that the first character on the 2nd line is
not a space and uses grouping \(...\) to save the first string of
non-space characters as \1 for the RHS. In writing any batch files,
make sure that output filenames such as GO_.BAT don't overwrite
preexisting files of the same name.
