.TH YESTERDAY 1
.SH NAME
yesterday, diffy \- print file names from the dump
.SH SYNOPSIS
.B yesterday
[
.B -abcCdDs
] [
.B -n
.I daysago
] [
.I \-date
]
.I files ...
.PP
.B diffy
[
.B -abcefmnrw
]
.I files ...
.SH DESCRIPTION
.I Yesterday
prints the names of the
.I files
from the most recent dump.
Since dumps are done early in the morning,
yesterday's files are really in today's dump.
For example, if today is March 17, 1992,
.IP
.EX
yesterday /adm/users
.EE
.PP
prints
.IP
.EX
/n/dump/1992/0317/adm/users
.EE
.PP
In fact, the implementation is to select the most recent dump in
the current year, so the dump selected may not be from today.
.PP
When presented with a path of the form
.BI /n/ fs / path \fR,
.I yesterday
will look for
dump files of the form
.BI /n/ fs dump/ yyyy / hhmm / path \fR.
.PP
By default, 
.I yesterday
prints the names of the dump files corresponding to the named files.
The first set of options changes this behavior.
.TP
.B -a
Run
.IR acme (1)'s
.I adiff
to compare the dump files with the named files.
.TP
.B -b
Bind the dump files over the named files.
.TP
.B -c
Copy the dump files over the named files.
.TP
.B -C
Copy the dump files over the named files only when
they differ.
.TP
.B -d
Run 
.B diff
to compare the dump files with the named files.
.TP
.B -D
Run 
.B diff
.B -n
to compare the dump files with the named files.
.PP
The
.I date
option selects other day's dumps, with a format of
1, 2, 4, 6, or 8 digits of the form
.IR d,
.IR dd ,
.IR mmdd ,
.IR yymmdd ,
or
.IR yyyymmdd .
.PP
The
.B -n
option selects the dump
.I daysago
prior to the current day.
.PP
The
.B -s
option selects the most recent snapshot instead of the most
recent archived dump.  Snapshots may occur more frequently
than dumps.
.PP
.I Yesterday
does not guarantee that the string it prints represents an existing file.
.PP
.I Diffy
runs
.IR diff (1)
with the given options
to compare yesterday's version of each of the named files
with today's.
.SH EXAMPLES
.PP
Back up to yesterday's MIPS binary of
.BR vc :
.IP
.EX
yesterday -c /mips/bin/vc
.EE
.PP
Temporarily back up to March 1's MIPS C library to see if a program
runs correctly when loaded with it:
.IP
.EX
yesterday -b -0301 /mips/lib/libc.a
rm v.out
mk
v.out
.EE
.PP
Find what has changed in the C library since March 1:
.IP
.EX
yesterday -d -0301 /sys/src/libc/port/*.c
.EE
.PP
Find what has changed in the source tree today:
.IP
.EX
diffy -r /sys/src
.EE
.SH FILES
.B /n/dump
.SH SOURCE
.B /rc/bin/yesterday
.br
.B /rc/bin/diffy
.SH SEE ALSO
.IR history (1),
.IR bind (1),
.IR diff (1),
.IR fs (4).
.SH BUGS
It's hard to use this command without singing.