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Meaning of ${1+"$@"}

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# 1  
Old 02-25-2015
Meaning of ${1+"$@"}
I am new to unix and i saw a sh file with below command.
Code:
exec gpg --homedir /web/gnupg --passphrase-fd 4 ${1+"$@"} 4< /web/gnupg.passphrase

Can you please expalin the mening of 4 ${1+"$@"} 4< line.

My understanding is pass phrase will be read from file gnupg.passphrase.

Thanks
Last edited by rbatte1; 02-25-2015 at 09:32 AM.. Reason: Added CODE & ICODE tags
# 2  
Old 02-25-2015
${1+"$@"} expands as, if $1 is not blank, feed it "$@", which is "all arguments, properly quoted and escaped".

Otherwise, it's left as blank.

You are correct it's reading from the file. I'm presuming they're feeding it into FD 4 via 4< to avoid interfering with standard input.
Last edited by Corona688; 02-25-2015 at 11:06 AM..
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