bash command sed is outputting an unexpected error

Question

I'm trying replace a word in a file using sed. In the same bash script I use the command :

sed -i "s/${list[$index]}/${phone}/g" $1

And it's working flawlessly on the first function, but the second function I wrote:

sed -i "s/${list[$index]}/${zipcode}/g" $1

Outputs this error:

sed: -e expression #1, char 0: no previous regular expression

I'm really desperate, I'm pretty sure that it's a dumb mistake I'm doing but I can't sort it out

is something like this zipcode=4763A5 it does not contains any special char, it contains only hex chars. The same applies to phone — domenic
– domenic, Commented Apr 6, 2017 at 14:15
Nope, only hex chars there too. I find it really strange because they are the same almost a copy/paste — domenic
– domenic, Commented Apr 6, 2017 at 14:19
Try with a different sed command separator (i.e sed -i "s|${list[$index]}|${zipcode}|g" $1). Also try to remove -i switch for testing and also try to replace $1 with the real file. Switch -i will not work if $1 is not a real valid file (avoid also relative paths) — George Vasiliou
– George Vasiliou, Commented Apr 6, 2017 at 14:21
Please include the exact output of printf '%q\n' "${list[$index]}" "${phone}" "${zipcode}" in your question. — chepner
– chepner, Commented Apr 6, 2017 at 14:25
Given that error, it looks like ${list[$index]} is the empty string. — William Pursell
– William Pursell, Commented Apr 6, 2017 at 17:02

Community · Accepted Answer · 2017-05-23 12:25:36Z

When the first half of a sed substitute command is empty:

sed 's//foo/' <<< bar

It returns this error:

sed: -e expression #1, char 0: no previous regular expression

Therefore, as William Pursell commented, there's a value of the ${list[@]} array that's empty, or maybe $index is out of the array's range.

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