UNIX for Dummies Questions & Answers

That code is broken in multiple ways.

First, since the first letter of the heredoc delimiter, EOF, is quoted with a backslash, there will be no substitutions made by the shell within the heredoc. This means that "${string}" will appear literally instead of "hello".

Second, the heredoc delimiter, "EOF", which marks the end of the data is missing.

Third, you need to add a write command, w, to save the changes.

Fourth, before you can use the write command, the text that's inserted needs to be terminated with a lone dot on a line.

It's not all bad news, though. The edit, e, command can be used to load a file into the buffer without invoking ed once per file. If there are a very large number of files, the efficiency of my approach could be improved by only calling ed once and using the for loop to pipe commands into it.

Code:

for f in *; do
        l=$(wc -l < "$f")
        [ $l -lt 400 ] && continue
        printf 'e %s\n0a\nthere are 400 lines in this file and %d bonus lines\n.\nw\n' "$f" $((l-400))
done | ed -s

While the printf could be made more readable with a "%s\n" format string, the clarity of the original heredoc is unmatched by either of

Code:

printf '%s\n' "e $f" 0a "there are 400 lines in this file and $((l-400)) bonus lines" . w

or

Code:

printf '%s\n' \
        "e $f" \
        0a \
        "there are 400 lines in this file and $((l-400)) bonus lines" \
        . \
        w

Bleh.

Regards,
Alister