Save faked timestamps to file, load faked timestamps from file

The files can be set using FAKETIME_SAVE_FILE and FAKETIME_LOAD_FILE
environment variables respectively.

1 files changed, 22 insertions, 1 deletions

diff --git a/README b/README
index 05fdafa..c726c35 100644
--- a/README
+++ b/README
@@ -19,6 +19,7 @@ Content of this file:
    g) Using the "faketime" wrapper script
    h) "Limiting" libfaketime
    i) Spawning an external process
+   j) Saving timestamps to file, loading them from file
 5. License
 6. Contact
 
@@ -424,11 +425,31 @@ This will run the "echo" command with the given parameter during the first
 time-related system function call that "myprogram" performs after running for 5
 seconds.
 
+4j) Saving timestamps to file, loading them from file
+--------------------------------
+
+Faketime can save faked timestamps to a file specified by FAKETIME_SAVE_FILE
+environment variable. It can also use the file specified by FAKETIME_LOAD_FILE
+to replay timestamps from it. After consuming the whole file faketime returns
+to using the rule set in FAKETIME variable, but the timestamp processes will
+start counting from will be the last timestamp in the file.
+
+The file stores each timestamp in a stream of saved_timestamp structs
+without any metadata or padding:
+
+/** Storage format for timestamps written to file. Big endian.*/
+struct saved_timestamp {
+  int64_t sec;
+  uint64_t nsec;
+};
+
+
+Faketime needs to be run using the faketime wrapper to use the files.
 
 5. License
 ----------
 
-FTPL has been released under the GNU Public License, GPL. Please see the
+FTPL has been released under the GNU Public License, GPL. Please see xthe
 included COPYING file.