How can I write a shell script, using only shell features (and the date command), to output the number of minutes that have elapsed in the current day?


Since date treats non-specifiers as literals you could use the format string to construct a simple arithmetic expression for the current number of minutes, and then evaluate the result using the shell's built-in arithmetic. For example, in bash

printf "$(( $(date '+%H * 60 + %M') ))\n"

If your shell does not support arithmetic, you could use an external calculator such as bc

date '+%H * 60 + %M' | bc

or dc

date '+%H 60 * %M + p' | dc

GNU date and bash:

daystart_sec="$(date --date="today 00:00:00" +%s)"
now_sec="$(date +%s)"
echo $(((now_sec-daystart_sec)/60))

how do I subtract the number of minutes passed in the day from the number of minutes left in the day (i.e., 1440)? So basically I want to subtract the output of the above from 1440.

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