Determining the last changelist synced to in Perforce

Question

I recommend the opposite for automatic build systems: you should first get the latest changelist from the server using:

p4 changes -s submitted -m1

then sync to that change and record it in the revision info. The reason is as follows. Although Perforce recommends the following to determine the changelist to which the workspace is synced:

p4 changes -m1 @clientname

they note a few gotchas:

• This only works if you have not submitted anything from the workspace in question.
• It is also possible that a client workspace is not synced to any specific changelist.

and there's an additional gotcha they don't mention:

• If the highest changelist to which the sync occured strictly deleted files from the workspace, the next-highest changelist will be reported (unless it, too, strictly deleted files).

If you must sync first and record later, Perforce recommends running the following command to determine if you've been bit by the above gotchas; it should indicate nothing was synced or removed:

p4 sync -n @changelist_number

Just to answer this myself in keeping with Jeff's suggestion of using Stackoverflow as a place to keep technical snippets....

From the command line use:

p4 changes -m1 @<clientname>

And just replace with the name of your client spec. This will produce output of the form:

Change 12345 on 2008/08/21 by joebloggs@mainline-client '....top line of description...'

Which is easily parsed to extract the changelist number.

You may try finding the maximum change number in the output of the "p4 files" command. The working directory should not contain post-sync commits, though. This is just a tad better than

p4 changes -m1 "./...#have"

as the latter seems to run on the server and may fail on big source trees due to "MaxResults" limits.

$ p4 changes -m1 "./...#have"
Request too large (over 850000); see 'p4 help maxresults'.

$ p4 -G files "./...#have" | python c:/cygwin/usr/local/bin/p4lastchange.py
Files: 266948
2427657

where p4lastchange.py is based on the code from the Using P4G.py From the Command Line presentation by J.T.Goldstone, Kodak Information Network/Ofoto, April 15, 2005.

#! /usr/bin/env python
import sys, os, marshal

if os.name == "nt":
    # Disable newline translation in Windows.  Other operating systems do not
    # translate file contents.
    import msvcrt
    msvcrt.setmode( sys.stdin.fileno(), os.O_BINARY )

lastcl = 0
num = 0
try:
    while 1:
        dict = marshal.load(sys.stdin)
        num = num + 1
        for key in dict.keys():
            # print "%s: %s" % (key,dict[key])
            if key == "change":
                cl = int(dict[key])
                if cl > lastcl:
                    lastcl = cl
except EOFError:
    pass
print "Files: %s" % num
print lastcl

If you are using P4V you can do this graphically:

• In the Dashboard tab (View->Dashboard) choose a folder and you will see a list of changelists that the folder isn't yet updated with. Note the lowest number (in the highest row).
• Make sure that in the Workspace Tree you have selected the same folder as previously in the Dashboard. Then go to the History tab (View->History) and scroll down to the number noted previously. The number just below that number is the number of your current changelist.

p4 changes -m1 @clientname which is the "recommended" way to do it for my client takes about 10 minutes

this is what I use:

p4 cstat ...#have | grep change | awk '$3 > x { x = $3 };END { print x }'

for the same client takes 2.1 seconds