bash tutorial and notes

1 files changed, 29 insertions, 24 deletions

diff --git a/software/bash.page b/software/bash.page
index 0a3f73f..088d456 100644
--- a/software/bash.page
+++ b/software/bash.page
@@ -1,43 +1,48 @@
 ---
-format: rst
+format: md
 toc: no
 ...
 
-==================
 BASH
 ==================
 
-Job Control
-    The syntax for "job number" or "JOBSPEC" (when using ``kill`` or similar) is ``%4`` or ``%5``.
 
-Startup
--------
-``bash`` by default takes a very long time to initialize because the
+# Tricks and Specifics
+
+## Job Control
+
+The syntax for "job number" or "JOBSPEC" (when using `kill` or similar) is
+`%4` or `%5`.
+
+
+## Startup
+
+`bash` by default takes a very long time to initialize because the
 auto-completion scripts are loaded multiple times; disable this in
-``~/.bashrc``?
+`~/.bashrc`?
+
+
+## Piping
 
-Piping
----------
-You can pipe both ``stdout`` and ``stderr`` together either to a file or two another command::
+You can pipe both `stdout` and `stderr` together either to a file or two another command::
 
     grep --asdf >& /some/file
     grep --asdf |& less
 
-Network Access
-----------------
-You can directly access network sockets as if they were files from bash using
-the virtual devices ``/dev/tcp/HOSTNAME/PORT`` and ``/dev/udp/HOSTNAME/PORT``.
 
-printf
-------
-The ``printf`` command is much more powerful than "echo".
+## printf
+
+The `printf` command is much more powerful than `echo`.
+
 
-Prelude
--------
+## Prelude
 
-`set`:
+I frequently add a one-line version of the following to shell scripts:
 
-    -e          fail on error
-    -u          fail if variable not set in substitution
-    -o pipefail fail if part of a '|' command fails
+    set -e              # fail on error
+    set -u              # fail if variable not set in substitution
+    set -o pipefail     # fail if part of a '|' command fails
 
+Note that `join`, `grep`, and others sometimes exit non-zero return codes on
+purpose (eg, pipe input closed or found no matches, as expected), which makes
+life difficult. Sometimes `|| true` is enough to get around this.