Fish Shell:
Calculating a date in the future or past

How to:

Here’s a cool way of rolling with dates in Fish Shell:

# Add days to the current date
set -l days_to_add 10
date -d "+$days_to_add days"

# Output example (varies by current date):
# Wed Mar 29 00:29:10 PDT 2023

# Subtract days from the current date
set -l days_to_subtract 10
date -d "-$days_to_subtract days"

# Output example (again, your date may vary):
# Sun Mar 9 00:30:42 PDT 2023

Deep Dive

Fish isn’t all about the splash; it comes with history. Shells like bash used to be the go-to for date calculations, typically through GNU date. Fish, keeping it streamlined, uses similar syntax but can be more user-friendly and readable – great for both swimming newbies and seasoned trout.

Alternatives for date calculations include programming languages like Python or using dateutils. Each has its own strengths, though dateutils is a bit more obscure and Python might be overkill for simple tasks. Implementation in Fish is a middle ground, with the date command borrowing from UNIX standards – it’s pretty much installed everywhere and ties into system time settings smoothly.

See Also

For more details, dive into these waters:

• GNU Coreutils – Date: Get a grasp of how date works under the hood.
• The Fish Shell Documentation: Official docs, where you can learn about Fish and its other commands.
• StackOverflow: Date Arithmetic: See real-world problems and solutions from the community.