Pipe string to GNU Date for conversion - how to make it read from stdin?

问题

GNU Date lets you convert date strings like so:

$ date +"%d %m %Y" -d "yesterday"
  04 01 2012

Is it possible to pipe a date string to it for conversion? I've tried the obvious -d - like so:

$ echo "yesterday" | date +"%d %m %Y" -d -

but it prints today's date instead of yesterdays.

Is it possible to pipe values to it or doesn't it support that?

Thanks.

回答1:

Yes.

 echo "yesterday" | xargs date +"%d %m %Y" -d

回答2:

date -f tells it to do the same thing as -d except for every line in a file... you can set the filename to - to make it read from standard input.

echo "yesterday" | date +"%d %m %Y" -f -

回答3:

You can use `command` or $(command) substitution:

date +"%d %m %Y" -d $(echo "yesterday")

回答4:

Just to throw it in, in bash:

date +"%d %m %Y" -f <(echo yesterday)

来源：https://stackoverflow.com/questions/8742476/pipe-string-to-gnu-date-for-conversion-how-to-make-it-read-from-stdin