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up vote 2 down vote favorite

I want to expand a variable in bash with sed or awk. This variable is an array.

For example, the script must delete strings contained in array. I tried

ARRAY1=(
string1
string2
string3
)

sed -i '/${ARRAY1[@]}/d'  /etc/file

and

ARRAY1=(
string1
string2
string3
)

for i  in ${ARRAY1[@]} ;do sed -i '/$i/d'  /etc/file;done

but none works, sed does not expand the variables.
How can I do this?

share|improve this question
    
the second solution would work if you used "" instead of '' as elbarna said. – Rob Oct 2 '14 at 12:33
up vote 3 down vote

With zsh:

array1=(
  string1
  string2
  string3
)
sed -i -e/$^array1/d file

Would delete all the lines that match any of the regex in $array1.

Or you could do (any Bourne-like shell):

regexps='string1
string2
string3'
grep -ve "$regexps" file

Or, to search strings, add the -F:

grep -F -v -e$^array1 # (zsh)

or:

strings='string1
string2
string3'
grep -F -ve "$strings" # (any shell)
share|improve this answer
up vote 1 down vote

Found solution, using "" instead of ''.

share|improve this answer
1  
It is true that "" will expand your variable for illustration try echo ${ARRAY1[@]}, echo '${ARRAY1[@]}' and echo "${ARRAY1[@]}" ... That said, just changing the quotes would not create the desired behavior as it would also print each element of the array in a separate lines and would at best not match what you intended at worse garble the sed command where it would cause a parsing error of the pattern. – Rob Oct 2 '14 at 12:29
up vote -1 down vote

I would not use sed instead use egrep -i -v (-i case insensitive -v does not match pattern):

egrep -i -v "$(echo ${ARRAY1[@]} | tr ' ' '|')" /etc/file

the expression 

echo ${ARRAY1[@]}

because it has no quotes will not print new line making a space delimited string with all the strings in the array.

tr ' ' '|'

will replace all spaces with \| (or) for the grep expression which will build the pattern for your grep command.

Now if you insist on using sed there are a couple of options one of which would look something like:

 sed -i $(echo ${ARRAY1[@]} | sed -e 's:\w\+:-e "/\1/d":g') /etc/file

This will create a separate -e "/stringFromArray/d" for the sed base sed command

NOTE: make sure that there are no spaces or "/$|" in the strings in your array. If there are depending on what solution you try it could get in the way.

share|improve this answer
2  
tr ' ' '\|' does not replace spaces by \|` but by `. tr` replaces characters, not strings. Not quoting ${ARRAY1[@]} is fundamentally problematic as it will break if there is whitespace or \[?* in any of the array elements. While the fundamental idea of using grep here is good, the execution needs to be rethought. – Gilles Oct 2 '14 at 20:59
    
Good point I was in a hurry and grep does not interpret | properly but egrep or grep -E does. so changed it to egrep and the tr to replace space with | and voila. – Rob Oct 3 '14 at 1:51

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