Merge pull request #1 from jlevy/master

merge commits

README.md

@@ -65,6 +65,8 @@ Notes:
 
 - Basic network management: `ip` or `ifconfig`, `dig`.
 
+- Learn and use a version control management system, such as `git`.
+
 - Know regular expressions well, and the various flags to `grep`/`egrep`. The `-i`, `-o`, `-v`, `-A`, `-B`, and `-C` options are worth knowing.
 
 - Learn to use `apt-get`, `yum`, `dnf` or `pacman` (depending on distro) to find and install packages. And make sure you have `pip` to install Python-based command-line tools (a few below are easiest to install via `pip`).
@@ -83,7 +85,9 @@ Notes:
 
 - To see recent commands, `history`. There are also many abbreviations such as `!$` (last argument) and `!!` last command, though these are often easily replaced with **ctrl-r** and **alt-.**.
 
-- To go back to the previous working directory: `cd -`
+- Go to your home directory with `cd`. Access files relative to your home directory with the `~` prefix (e.g. `~/.bashrc`). In `sh` scripts refer to the home directory as `$HOME`.
+
+- To go back to the previous working directory: `cd -`.
 
 - If you are halfway through typing a command but change your mind, hit **alt-#** to add a `#` at the beginning and enter it as a comment (or use **ctrl-a**, **#**, **enter**). You can then return to it later via command history.
 
@@ -110,6 +114,12 @@ Notes:
 
 - Use `alias` to create shortcuts for commonly used commands. For example, `alias ll='ls -latr'` creates a new alias `ll`.
 
+- Save aliases, shell settings, and functions you commonly use in `~/.bashrc`, and [arrange for login shells to source it](http://superuser.com/a/183980/7106). This will make your setup available in all your shell sessions.
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+- Put the settings of environment variables as well as commands that should be executed when you login in `~/.bash_profile`. Separate configuration will be needed for shells you launch from graphical environment logins and `cron` jobs.
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+- Synchronize your configuration files (e.g `.bashrc` and `.bash_profile`) among various computers with Git.
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 - Understand that care is needed when variables and filenames include whitespace. Surround your Bash variables with quotes, e.g. `"$FOO"`. Prefer the `-0` or `-print0` options to enable null characters to delimit filenames, e.g. `locate -0 pattern | xargs -0 ls -al` or `find / -print0 -type d | xargs -0 ls -al`. To iterate on filenames containing whitespace in a for loop, set your IFS to to be a newline only using `IFS=$'\n'`.
 
 - In Bash scripts, use `set -x` (or the variant `set -v`, which logs raw input, including unexpanded variables and comments) for debugging output. Use strict modes unless you have a good reason not to: Use `set -e` to abort on errors (nonzero exit code). Use `set -u` to detect unset variable usages. Consider `set -o pipefail` too, to on errors within pipes, too (though read up on it more if you do, as this topic is a bit subtle). For more involved scripts, also use `trap` on EXIT or ERR. A useful habit is to start a script like this, which will make it detect and abort on common errors and print a message:
@@ -204,6 +214,8 @@ Notes:
 
 - Know that locale affects a lot of command line tools in subtle ways, including sorting order (collation) and performance. Most Linux installations will set `LANG` or other locale variables to a local setting like US English. But be aware sorting will change if you change locale. And know i18n routines can make sort or other commands run *many times* slower. In some situations (such as the set operations or uniqueness operations below) you can safely ignore slow i18n routines entirely and use traditional byte-based sort order, using `export LC_ALL=C`.
 
+- You can set a specific command's environment by prefixing its invocation with the environment variable settings, as in `TZ=Pacific/Fiji date`.
+
 - Know basic `awk` and `sed` for simple data munging. For example, summing all numbers in the third column of a text file: `awk '{ x += $3 } END { print x }'`. This is probably 3X faster and 3X shorter than equivalent Python.
 
 - To replace all occurrences of a string in place, in one or more files: