How do I use vim within a Unix pipe-line?

Question

I can use vim / ex to grep a file using the following invocation:

ex -c'g/foo/p' -cq -s afile.txt

I'd really like to use a similar command to grep some text from stdin. I thought the following command should work, but it produces no output:

cat afile.txt | ex -c'g/foo/p' -cq -s -

The same thing happens if I use vim -e instead of ex:

cat test.md | vim -e -c'g/foo/p' -cq -s -

Is there any way that I can force ex to read its initial buffer from stdin and print output to stdout, so that it can be used within a Unix pipe-line?

Answer 1

Move the special filename - before -e:

cat test.md | vim -e -c'g/foo/p' -cq -s -
                                        ^
                                        ✘

cat test.md | vim - -e -c'g/foo/p' -cq -s
                  ^
                  ✔

Before -e, - is read as literal text. After -e, - is read as an Ex command.

---

To suppress the Vim: Reading from stdin... warning, pass the --not-a-term argument to the vim(1) command:

cat test.md | vim - -e -c'g/foo/p' -cq -s --not-a-term
                                          ^----------^

---

To make Vim quit, execute :qa! instead of just :q:

cat test.md | vim - -e -c'g/foo/p' +'qa!' -s --not-a-term
                                     ^-^

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You can join -e and -s, and you can replace -c with +:

cat test.md | vim - -es +'g/foo/p' +'qa!' --not-a-term
                      ^ ^

You should now be able to pass Vim's output to another shell utility; e.g. wc(1):

cat test.md | vim - -es +'g/foo/p' +'qa!' --not-a-term | wc -l
                                                       ^-----^

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See also:

• vims
• Vim for pipeline filtering
• Vim's social life
• my notes