Newline-Separated List to Comma-Separated List

Convert a newline-separated list into a single-line comma-separated list with quoted entries:

$EXEC_STUFF | sed 's/^\\|$/"/g' | paste -sd, -

How it works:

1. sed 's/^\\|$/"/g' — wraps each line in double quotes (^ = start, $ = end)
2. paste -sd, - — serial merge (-s) using , as the delimiter (-d), reading from stdin (-)

Example:

$ printf 'foo\nbar\nbaz\n' | sed 's/^\\|$/"/g' | paste -sd, -
"foo","bar","baz"

Platform note: On GNU/Linux (coreutils), the trailing - can be omitted. On macOS and other POSIX systems, include the - to read from stdin.

DOS line endings: If the input has \r\n line endings, strip the \r first:

sed 's/\r//;s/^\\|$/"/g' | paste -sd, -

Comma+space separator: To get "foo", "bar", "baz" instead, use a two-step paste pipeline (see the raw source for the pure-paste approach) or switch to awk:

awk 'BEGIN { ORS="" } { print p"\047"$0"\047"; p=", " } END { print "\n" }' file.txt

The paste approach is notably fast — the kernel’s pipe handling makes it competitive with compiled tools for this task.

Related

• sed-single-line-find-replace — sed one-liner patterns
• bash-scripting — general shell text processing

Sources

• Unix SE: Turning lines into a comma-separated list
• paste(1) man page