Shell Script error: “head: invalid trailing option — 1”

Question

I have this code in my shell(bash) script for splitting a file into smaller parts:

for (( i=$start; i<=$lineCount; i=i+$interval))
do
    temp=`expr $i + $int         


        

Answer 1

When you put the pipe | in a variable, the shell interprets it as an ordinary character and not as a pipe. Ditto for redirection operators like >, <, ...

An ugly way would be to use eval.

A better approach would be to split your command into different parts so as to get rid of pipes and redirection operators in it.

For example:

command="head -$temp $fileName | tail -$lastLines > tmpFileName";

would be written as:

cmd1="head -$temp $fileName";
cmd2="tail -$lastLines";

and executed by saying:

"$cmd1" | "$cmd2" > tmpFileName;

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Moreover, you don't need backticks to execute a command that is stored in a variable. Simply say:

$command