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I'm been playing around with SQlite at work, specifically with trying to get the sqlite3 command line tool to accept stdin instead of a file. Sounds easy enough, on linux you can execute a command like:

echo 'test' | sqlite3 test.db '.import /dev/stdin test'

unfortunately - our machines at work run AIX (5 & 6) and as far as I can tell, there is no equivalent to the virtual file /dev/stdin. I managed to hack together an equivalent command that works on AIX using a temporary file.

echo 'test' | cat - > /tmp/blah ; sqlite3 test.db '.import /tmp/blah test' ; rm /tmp/blah

Now, does it need to use STDIN? isn't this temporary file thing enough? Probably, but I was hoping someone with better unix-fu had a more elegant solution.

note: the data I would like to import is only provided via STDOUT, so that's what the echo 'test' command is all about.

Clarification - I only have control over commands on the Right Hand Side of the pipe shown above. The data is being processed, and then passed to my command via stdin/stdout. the echo 'test' command is illustrative only.

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  • I'm assuming there's a typo in your second command. Where it says "/dev/stdin" should it say "/tmp/blah"?
    – Dennis Williamson
    Jun 9, 2010 at 11:23
  • hahhah - yeah it totally should, i reread that a bunch of times.
    – mikfreedman
    Jun 9, 2010 at 13:16
  • Does AIX have /dev/fd/? If so, then /dev/fd/0 should be the same as /dev/stdin.
    – larsks
    Nov 18, 2010 at 2:47

3 Answers 3

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If you're actually using Bash and AIX supports process substitution (which I believe is platform dependent), this might work for you:

Demo:

cat <(echo 'test')

Your command:

sqlite3 test.db '.import '<(echo test)' test'
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  • the echo test bit unfortunately isn't another unix command line tool - it's some random program that communicates via stdin/stdout, but has a convoluted execution framework that wouldn't allow it to be called that way, if that makes sense.
    – mikfreedman
    Jun 9, 2010 at 13:18
  • @mikfreedman: I don't understand. If it can be called in a pipeline, it can be called using process substitution. Also, in your second command in your question why use cat -? Why not echo 'test' > /tmp/blah?
    – Dennis Williamson
    Jun 9, 2010 at 13:43
  • in the program I am using, I can enter a unix command that the program will write to, the only requirement is this program can only write to STDOUT.. so, it's arriving at my arbitrary command via a pipe, but the order must be as I described. For reference the program I am using is Infosphere DataStage.
    – mikfreedman
    Jun 9, 2010 at 14:08
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Based on the answers above:

... | sqlite3 test.db 'import '<(cat -)' test'

I've tested this on my system and it appears to do what you want.

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If the STDIN hacks aren't working on that platform, how about using a named pipe instead of the temp file? It'd behave from the perspective of the two programs like a file, but without the actual writing to and reading from disk.

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