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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:38:56 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:38:56 +0000 |
commit | 6c20c8ed2cb9ab69a1a57ccb2b9b79969a808321 (patch) | |
tree | f63ce19d57fad3ac4a15bc26dbfbfa2b834111b5 /examples/scripts/bcalc | |
parent | Initial commit. (diff) | |
download | bash-upstream.tar.xz bash-upstream.zip |
Adding upstream version 5.2.15.upstream/5.2.15upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | examples/scripts/bcalc | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/examples/scripts/bcalc b/examples/scripts/bcalc new file mode 100644 index 0000000..bc7e2b4 --- /dev/null +++ b/examples/scripts/bcalc @@ -0,0 +1,104 @@ +#! /bin/bash +# +# bcalc - a coproc example that uses bc to evaluate floating point expressions +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +# +# If supplied command-line arguments, it uses them as the expression to have +# bc evaluate, and exits after reading the result. Otherwise, it enters an +# interactive mode, reading expressions and passing them to bc for evaluation, +# with line editing and history. +# +# You could even use this to write bc programs, but you'd have to rework the +# single-line REPL a little bit to do that (and get over the annoying timeout +# on the read) +# +# Chet Ramey +# chet.ramey@case.edu + +# we force stderr to avoid synchronization issues on calculation errors, even +# with the read timeout +init() +{ + coproc BC { bc -q 2>&1; } + # set scale + printf "scale = 10\n" >&${BC[1]} + # bash automatically sets BC_PID to the coproc pid; we store it so we + # can be sure to use it even after bash reaps the coproc and unsets + # the variables + coproc_pid=$BC_PID +} + +# not strictly necessary; the pipes will be closed when the program exits +# but we can use it in reset() below +fini() +{ + eval exec "${BC[1]}>&- ${BC[0]}<&-" +} + +reset() +{ + fini # close the old pipes + + sleep 1 + kill -1 $coproc_pid >/dev/null 2>&1 # make sure the coproc is dead + unset coproc_pid + + init +} + +# set a read timeout of a half second to avoid synchronization problems +calc() +{ + printf "%s\n" "$1" >&${BC[1]} + read -t 0.5 ANSWER <&${BC[0]} +} + +init + +# if we have command line options, process them as a single expression and +# print the result. we could just run `bc <<<"scale = 10 ; $*"' and be done +# with it, but we init the coproc before this and run the calculation through +# the pipes in case we want to do something else with the answer + +if [ $# -gt 0 ] ; then + calc "$*" + printf "%s\n" "$ANSWER" + fini + exit 0 +fi + +# we don't want to save the history anywhere +unset HISTFILE + +while read -e -p 'equation: ' EQN +do + case "$EQN" in + '') continue ;; + exit|quit) break ;; + reset) reset ; continue ;; + esac + + # save to the history list + history -s "$EQN" + + # run it through bc + calc "$EQN" + if [ -n "$ANSWER" ] ; then + printf "%s\n" "$ANSWER" + fi +done +fini + +exit 0 |