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Diffstat (limited to 'doc/coreutils.texi')
| -rw-r--r-- | doc/coreutils.texi | 37 |
1 files changed, 25 insertions, 12 deletions
diff --git a/doc/coreutils.texi b/doc/coreutils.texi index 1519fcb3e..7d32af582 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -9001,23 +9001,36 @@ occur on disk based devices): dd conv=noerror,sync iflag=fullblock </dev/sda1 > /mnt/rescue.img @end example -Sending an @samp{INFO} signal to a running @command{dd} -process makes it print I/O statistics to standard error -and then resume copying. In the example below, -@command{dd} is run in the background to copy 10 million blocks. +Sending an @samp{INFO} signal (or @samp{USR1} signal where that is unavailable) +to a running @command{dd} process makes it print I/O statistics to +standard error and then resume copying. In the example below, +@command{dd} is run in the background to copy 5GB of data. The @command{kill} command makes it output intermediate I/O statistics, and when @command{dd} completes normally or is killed by the @code{SIGINT} signal, it outputs the final statistics. @example -$ dd if=/dev/zero of=/dev/null count=10MB & pid=$! -$ kill -s INFO $pid; wait $pid -3385223+0 records in -3385223+0 records out -1733234176 bytes (1.7 GB) copied, 6.42173 seconds, 270 MB/s -10000000+0 records in -10000000+0 records out -5120000000 bytes (5.1 GB) copied, 18.913 seconds, 271 MB/s +# Ignore the signal so we never inadvertently terminate the dd child. +# Note this is not needed when SIGINFO is available. +trap '' USR1 + +# Run dd with the fullblock iflag to avoid short reads +# which can be triggered by reception of signals. +dd iflag=fullblock if=/dev/zero of=/dev/null count=5000000 bs=1000 & pid=$! + +# Output stats every half second +until ! kill -s USR1 $pid 2>/dev/null; do sleep .5; done +@end example + +The above script will output in the following format + +@example +859+0 records in +859+0 records out +4295000000 bytes (4.3 GB) copied, 0.539934 s, 8.0 GB/s +1000+0 records in +1000+0 records out +5000000000 bytes (5.0 GB) copied, 0.630785 s, 7.9 GB/s @end example @vindex POSIXLY_CORRECT |