The gotcha of logging gdb output

By default, gdb‘s output file is appended, not overwrote. E.g: debug the same program for 2 times:

$ gdb foo
......
(gdb) set logging on
Copying output to gdb.txt.
Copying debug output to gdb.txt.
(gdb) r
......
$ ll gdb.txt
-rw-rw-r-- 1 nanxiao nanxiao 1067 Jul  9 18:06 gdb.txt
$ gdb foo
......
(gdb) set logging on
Copying output to gdb.txt.
Copying debug output to gdb.txt.
(gdb) r
......
$ ll gdb.txt
-rw-rw-r-- 1 nanxiao nanxiao 2134 Jul  9 18:08 gdb.txt

After second debug, the gdb.txt‘s size is doubled. To overwrite the output file, execute set logging overwrite on before set logging on:

$ gdb foo
......
(gdb) set logging overwrite on
(gdb) set logging on
Copying output to gdb.txt.
Copying debug output to gdb.txt.
(gdb) r
......
$ ll gdb.txt
-rw-rw-r-- 1 nanxiao nanxiao 1067 Jul  9 18:10 gdb.txt