Boot time labs: use "-o" in grabserial to copy output to files

Instead of copying and pasting from the terminal.

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>

labs/boot-time-application/boot-time-application.tex

@@ -261,8 +261,8 @@ \section{Putting things back together}
       something on the screen to make the user wait.
 \end{itemize}
 
-Update and reboot your system through \code{grabserial}, and copy and
-paste your output to \code{boot-time-labs/logs/application.log}.
+Update and reboot your system through \code{grabserial}, copying the
+output to \code{~/logs/application.log}.
 Fill the below table with updated figures:
 
 \begin{tabular}{| l | l | r |}

labs/boot-time-filesystem-optimizations/boot-time-filesystem-optimizations.tex

@@ -30,8 +30,8 @@ \section{Tests with ext4 and SquashFS}
 Go to \code{~/boot-time-labs/rootfs}. You should have a \code{rootfs}
 subdirectory where your root filesystem archive has been extracted.
 
-Boot your system with \code{grabserial}, store its output in
-\code{logs/filesystem-ext4.log}, and start filling the table below:
+Boot your system with \code{grabserial}, copying its output to
+\code{~/logs/filesystem-ext4.log}, and start filling the table below:
 
 \begin{tabular}{| l | l | l | r |}
   \hline

labs/boot-time-init-scripts/boot-time-init-scripts.tex

@@ -395,7 +395,7 @@ \subsection{Testing}
 Boot your system again.
 
 If everything works, it's time to boot the system again through
-\code{grabserial}, store the output to \code{logs/init-scripts.log}
+\code{grabserial}, copying the output to \code{~/logs/init-scripts.log}
 and update the below table:
 
 \begin{tabular}{| l | l | r |}

labs/boot-time-software-measurement/boot-time-software-measurement.tex

@@ -104,11 +104,19 @@ \section{Timing the launching of the application}
 getting the new message. You can now measure the time between starting
 \code{ffmpeg} and finishing processing the first frame.
 
+Before running \code{grabserial} again, let's create the {\code
+$HOME/logs/} in which we will store copies of the command's output:
+
+\begin{verbatim}
+mkdir ~/docs/
+\end{verbatim}
+
 Thanks to the last message, we can now stop \code{grabserial} when it's
 received, replacing the \code{-e} argument:
 
 \begin{verbatim}
-grabserial -d /dev/ttyUSB0 -m "U-Boot SPL" -t -e 30 -q "First frame decoded"
+grabserial -d /dev/ttyUSB0 -m "U-Boot SPL" -t -e 30 -q "First frame decoded" \
+           -o ~/logs/initial.log
 \end{verbatim}
 
 We now have a complete measurement of the initial boot time of the
@@ -118,10 +126,6 @@ \section{Timing the launching of the application}
 are surprising and could have been copied in a wrong way, and
 investigate some differences between two different runs.
 
-So, create the {\code $HOME/boot-time-labs/logs} directory and copy and
-paste the \code{grabserial} output to the \code{initial.log} file in
-this directory.
-
 \section{Initial measurements}
 
 Now, take your calculator and fill the below table with the results from your experiments: