diffy [ -abcefmnrw ] files ...

yesterday /adm/users

prints

/n/dump/1992/0317/adm/users

In fact, the implementation is to select the most recent dump in the current year, so the dump selected may not be from today.

When presented with a path of the form /n/fs/path, yesterday will look for dump files of the form /n/fsdump/yyyy/hhmm/path.

By default, yesterday prints the names of the dump files corresponding to the named files. The first set of options changes this behavior.

-a

Run acme(1)'s adiff to compare the dump files with the named files.

-b

Bind the dump files over the named files.

-c

Copy the dump files over the named files.

-C

Copy the dump files over the named files only when they differ.

-d

Run diff to compare the dump files with the named files.

-D

Run diff -n to compare the dump files with the named files.

The date option selects other day's dumps, with a format of 1, 2, 4, 6, or 8 digits of the form d, dd, mmdd, yymmdd, or yyyymmdd.

The -n option selects the dump daysago prior to the current day.

The -s option selects the most recent snapshot instead of the most recent archived dump. Snapshots may occur more frequently than dumps.

Yesterday does not guarantee that the string it prints represents an existing file.

Diffy runs diff(1) with the given options to compare yesterday's version of each of the named files with today's.

yesterday -c /mips/bin/vc

Temporarily back up to March 1's MIPS C library to see if a program runs correctly when loaded with it:

yesterday -b -0301 /mips/lib/libc.a rm v.out mk v.out

Find what has changed in the C library since March 1:

yesterday -d -0301 /sys/src/libc/port/*.c

Find what has changed in the source tree today:

diffy -r /sys/src