Re: One liner to test existance of a file

"perl -e /.firstboot | echo $?"
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has a number of problems.

$? is interpolated before ssh and thus the shell will ever see it.
Perl doesn't accept a program on the command line unless you use its -e option.
String literals generally need to be quoted in Perl.
You never tell Perl to exit with an error, so $? will never be set properly.

The above should be

q{perl -e'exit(-e "/.firstboot" ?1:0)' | echo $?}
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which can be simplified to

q{perl -e'print -e "/.firstboot" ?1:0'}
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But why not just use the shell?

q{test ! -e /.firstboot ; echo $?}
   -or-
q{if [ -e /.firstboot ] ; then echo 1 ; else echo 0 ; fi}
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Also, you didn't specify what should be returned when it cannot be determined whether the file exists or not.

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Re^2: One liner to test existance of a file by kamal (Sexton) on Jul 15, 2010 at 01:02 UTC
if i use `q{if [ -e /.firstboot ] ; then echo 1 ; else echo 0 ; fi}` [download] i get: 0 root@baseline-dc1:~# The required output should be: 0 with NO new line, or carriage return, or space. somehow (i think) due to Net::SSH::Expect the prompt of the remote system is being appended to $stat hence i need to remove it	[reply] [d/l]
Re^3: One liner to test existance of a file by ikegami (Patriarch) on Jul 15, 2010 at 02:55 UTC
That command does not output that at all. `-n` prevents `echo` from outputting a newline. As for the prompt, it comes from the shell. Don't run a shell interactively, hide its prompt, waitfor it, or `exec` a shell to execute the command, causing the connection to drop after the output has been obtained.	[reply] [d/l] [select]