UNIX for Dummies Questions & Answers

Hi All,
I need to compare the header of the input files which can be comma demilited, tild(~) or Pipr(|) seperated file.
I am comparing the file header by taking 1st row and comparing it with input row:
Below is the actual codeksh script)

Code:

if [ $v_avilableheader -ne $v_header ]
    then
      echo  $dat >> $v_logdir/$v_logfile
    echo ":Header's doesn't match for the file $v_available_file_name" >> $v_logdir/$v_logfile
     mv $v_finalsourcefile $v_invalidfiledir
    v_errmessage="Header's doesn't match for the file $v_available_file_name"
exit
fi

=====================================================
output error:

Code:

--------------
+ [ "MEMBER"|"MEMBERDESC"|"LEVEL0"|"LEVEL1" -ne "MEMBER"|"MEMBERDESC"|"LEVEL0"|"LEVEL1" ]

./abcd.sh[208]: "MEMBER"|"MEMBERDESC"|"LEVEL0"|"LEVEL1": syntax error

====================================================

It says syntax error. Please help as to how to i compare both the variables..

Replace

Code:

if [ $v_avilableheader -ne $v_header ]

with

Code:

if [[ $v_avilableheader != "$v_header" ]]

.

Here is the problem: always keep in mind that the shell will do a simple text replacement to replace variables with their contents. This is very versatile on one hand but can lead to unexpected behaviour on the other.

Consider the following lines:

Code:

variable="abc 123"
command $variable

When the shell executes this it shell will first replace "$variable" with "abc 123", only then execute "command abc 123". It would even be possible to "execute" a variables contents directly:

Code:

variable="ls -l"
$variable

This replacement process is done in several different steps. Look up the details under "command evaluation [in the] Korn shell".

Your variable contents now contain the pipe-symbol ("|"), which is part of the regular shell syntax. After the replacement phase the shell will end up with a command which looks like a pipeline (but of course can't be executed). This is the reason for the syntax error.

The trick is to prevent the shell from interpreting the contents of your variables so it can't confuse these with command parts. This is why elixir_sinari suggested the double quotes around the variable names - they do exactly this.

I hope this helps.

bakunin

thanks it works fine now.

Just as a quote is not special when it appears during the parameter expansion parsing phase, the pipe symbol is not in any way special here. The parsing step which looks for quotes, pipes, and other operators has completed.

Code:

$ x='"A"|"B"|"C"'  # Unless eval is used, neither the pipes nor double quotes are special
$ echo $x
"A"|"B"|"C"
$ [ $x = '"A"|"B"|"C"' ] && echo MATCH
MATCH
$ $x
-bash: "A"|"B"|"C": command not found

Note that in that last case the entire string is a single token. Quotes and pipes were taken literally.

The OP's syntax error is most likely from passing string operands to an arithmetic operator, -ne.

Regards,
Alister