Combining wget and zenity/yad

问题

I'm trying to provide some kind of a GUI for wget download process by using zenity/yad. I have come up with this:

wget http://example.com/ 2>&1 | \
sed -u 's/^[a-zA-Z\-].*//; s/.* \{1,2\}\([0-9]\{1,3\}\)%.*/\1\n#Downloading... \1%/; s/^20[0-9][0-9].*/#Done./' | \
zenity --progress --percentage=0 --title=Download dialog --text=Starting... --auto-close --auto-kill

Now, suppose wget runs into an error. I need to inform the user that the download failed. Since the $? variable seems to have a value of 0 regardless of success or failure (perhaps because $? is storing zenity's exit status?), I can't tell if the download failed or succeeded.

How can I rectify the above described problem?

回答1:

You can say:

set -o pipefail

Saying so would cause $? to report the exit code of the last command in the pipeline to exit with a non-zero status.

Quoting from The Set Builtin:

pipefail

If set, the return value of a pipeline is the value of the last (rightmost) command to exit with a non-zero status, or zero if all commands in the pipeline exit successfully. This option is disabled by default.

---

Additionally, the array PIPESTATUS would report the return code of all the commands in the pipeline. Saying:

echo "${PIPESTATUS[@]}"

would list all those. For your example, it'd display 3 numbers, e.g.

1 0 0

if wget failed.

Quoting from the manual:

PIPESTATUS

An array variable (see Arrays) containing a list of exit status values from the processes in the most-recently-executed foreground pipeline (which may contain only a single command).

来源：https://stackoverflow.com/questions/21182937/combining-wget-and-zenity-yad