Date and Time Inputs

Date Format

Check the Shape

Scripts often receive dates from arguments or configuration. A lightweight format check catches obvious mistakes before the value reaches a file name or command.

Program

Play the script to choose a date string and see whether it passes the shape check.

date_format_check.sh 
#!/usr/bin/env bash

run_date=
if [[ "$run_date" == ????-??-?? ]]; then
    status="iso-date"
else
    status="bad-date"
fi
echo "$run_date:$status"

#!/usr/bin/env bash

run_date=
if [[ "$run_date" == ????-??-?? ]]; then
    status="iso-date"
else
    status="bad-date"
fi
echo "$run_date:$status"
ISO date `YYYY-MM-DD` is easy to sort and compare as text.
shape check A shape check catches values that are plainly not in the expected format.
input boundary Validate date text at the boundary before building paths or commands.