Question

I tried to insert a text to the first line
of a file using sed. I do this inside a sh
script.

But why it hangs at the line of sed execution?

#! /bin/sh

# Command to execute
# ./mybashcode.sh test.nbq

nbqfile=$1   
nbqbase=$(basename $nbqfile nbq)
taglistfiletemp="${nbqbase}taglist_temp"
taglistfile="${nbqbase}taglist"


./myccode $nbqfile | 
sort | 
uniq -c | 
awk '{print $2}' > $taglistfiletemp 

noftags=$(wc -l $taglistfiletemp | awk '{print $1}')
echo $noftags


# We want to append output of noftags
# to the first line of taglistfile

sed '1i\
$noftags' > $taglistfile

# why it hangs here
# the content of taglistfile is NIL

Answer 1

I’m not sure what you are trying to do with sed but it needs two inputs, the script (usually a search/replace) and the data you want to perform it on. If you only specify one it assumes it has got the regular expression and waits for data on stdin. As you haven’t supplied anything on stdin it’ll hang indefinitely.

In addition, you have ‘$noftags‘ rather than “$noftags“. The prior will output $noftags and the latter the contents of the variable, as single quotes do not allow variable expansion.