Update cheatsheets

cat

@@ -0,0 +1,29 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# cat
+
+> Print and concatenate files.
+> More information: <https://manned.org/cat.1posix>.
+
+- Print the contents of a file to `stdout`:
+
+`cat {{path/to/file}}`
+
+- Concatenate several files into an output file:
+
+`cat {{path/to/file1 path/to/file2 ...}} > {{path/to/output_file}}`
+
+- Append several files to an output file:
+
+`cat {{path/to/file1 path/to/file2 ...}} >> {{path/to/output_file}}`
+
+- Copy the contents of a file into an output file without buffering:
+
+`cat -u {{/dev/tty12}} > {{/dev/tty13}}`
+
+- Write `stdin` to a file:
+
+`cat - > {{path/to/file}}`