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Bash error message for unterminated heredoc is unhelpful.


From: Richard Neill
Subject: Bash error message for unterminated heredoc is unhelpful.
Date: Sat, 28 Jun 2008 20:49:58 +0100
User-agent: Thunderbird 2.0.0.12 (X11/20080306)

Dear All,

In some cases, bash gives exceptionally unhelpful error messages, of the
sort "Unexpected end of file". This is next-to-useless as a debugging
aid, since there is no way to find out where the error really lies.

I'm using bash version: bash-3.2-7mdv2008.1

Here are 2 shell scripts with examples.
   bug-example.sh   demonstrates the problem.
   bug-example2.sh  is where bash gets it right.

Thanks very much,

Richard



address@hidden ~]$ cat bug-example.sh
-------------------------------------------------------------
#!/bin/bash

#This is an example of bash being unhelpful with syntax errors.

function usage () {
        cat <<-EOT
                This help text is a heredoc
        EOT
        #NOTE that the line above contains a trailing TAB, and
        # is therefore NOT valid as the end of the heredoc.
}

usage

echo "A long script goes here..."

echo "Many lines later..."

exit 0


#This script generates the following error:
#     ./bug-example.sh: line 37: syntax error: unexpected end of file
#That is really not helpful, since there's no way to track down where
#the error started. Line 37 is not interesting. What we need is a
#warning about line 6.

#At a minimum, we should get this error message:
#     ./bug-example.sh: line 37: syntax error: unexpected end of file
#      (started at line 6)

#Better, would be this error message:
#     ./bug-example.sh: line 6: syntax error: unterminated heredoc.

#An additional buglet is that in fact, trailing whitespace after
#a heredoc terminator should probably be ignored anyway?
-------------------------------------------------------------




address@hidden ~]$ cat bug-example2.sh
-------------------------------------------------------------
#!/bin/bash

#This is an example of bash being *helpful* with syntax errors.

X=$((1 + 2)                     #NOTE missing trailing ).

echo "X is $X"                  #Should print 'X is 3'


echo "A long script goes here..."
echo "Many lines later..."
exit 0

#This script gets it right with the error message.
#     ./bug-example2.sh: line 5: unexpected EOF while looking for
#      matching `)'
#      ./bug-example2.sh: line 20: syntax error: unexpected end of file

#So, we can quickly find the bug.
-------------------------------------------------------------







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