Add Grab The First Line Of A File as a sed til

sed/grab-the-first-line-of-a-file.md

@@ -0,0 +1,29 @@
+# Grab The First Line Of A File
+
+You can grab the first line of a file with `sed` using either the `p` (print)
+command or the `d` (delete) command.
+
+First, the _print_ command can be told to print the line matching the line
+number `1`. That combined with the `-n` flag, which suppresses all lines not
+explicitly printed, will print just the first line in the file.
+
+```bash
+$ sed '1 p' README.md
+# TIL
+```
+
+Second, the _delete_ command can be told to delete all lines that aren't the
+first (`1`) line.
+
+```bash
+$ sed '1! d' README.md
+# TIL
+```
+
+The `1` will match on the first line. By following it with `!`, that will
+negate it so that it represents all lines except `1`.
+
+See `man sed` for more details.
+
+Note: there are more efficient ways, not using `sed`, to get the first line in
+a file. This is an exercise in using and understanding some `sed` features.