Merge pull request #102 from terminalforlife/master

Code, Formatting Tweaks, Some Fixes, Headers, etc

sheets/airport

@@ -1,15 +1,14 @@
 # airport
-#
 # Wireless network configuration utility.
 
-# Show current wireless status information:
+# Show current wireless status information.
 airport -I
 
-# Sniff wireless traffic on channel 1:
+# Sniff wireless traffic on channel 1.
 airport sniff 1
 
-# Scan for available wireless networks:
+# Scan for available wireless networks.
 airport -s
 
-# Disassociate from current airport network:
-sudo airport -z
+# Disassociate from current airport network.
+airport -z

sheets/apk

@@ -1,23 +1,24 @@
-# apk is the tool used to install, upgrade, or delete software on a running system
-# of Alpine Linux package management
+# apk
+# Package management software for use in Alpine Linux
 
-# Install a package
-apk add $package
+# Install a package, or upgrade an existing one.
+apk add [PKG]
 
 # Remove a package
-apk del $package
+apk del [PKG]
 
-# Update repos
+# Update index of available packages.
 apk update
 
-# Upgrade all packages
+# Upgrade all installed packages.
 apk upgrade
 
-# Find a package
-apk search $package
+# Find package, using glob pattern matching.
+apk search [PKG]
 
-# To list all installed packages, use:
+# List all installed packages.
 apk info
 
-# To determine which package a file belongs to:
-apk info --who-owns /sbin/lbu
+# Determine to which package a file belongs, akin to `dpkg -S [PATH]` in
+# Debian- and Ubuntu-based distributions of Linux.
+apk info --who-owns [PATH]

sheets/apt-cache

@@ -1,9 +1,12 @@
-# Search for package PKG. Both package names and their descriptions are searched
-# for a REGEX match; to avoid this behavior, you may use the `-n` flag, which will
-# only look for a match in the package name.
+# apt-cache
+# Query the APT cache
+
+# Search for package PKG. Both package names and their descriptions are
+# searched for a REGEX match; to avoid this behavior, you may use the `-n`
+# flag, which will only look for a match in the package name.
 apt-cache search 'PKG'
 
-# Regarding the above, although multiple package names may not be specified, it's
-# possible to use ERE to easily and quickly get around this limitation. Here, all
-# 3 packages (PKG1, PKG2, and PKG3) will be sought.
+# Regarding the above, although multiple package names may not be specified, -
+# it's possible to use ERE to easily and quickly get around this limitation.
+# Here, all 3 packages (PKG1, PKG2, and PKG3) will be sought.
 apt-cache search '(PKG1|PKG2|PKG3)'

sheets/apt-get

@@ -1,17 +1,20 @@
-# Update the local database of available packages, as discovered from package index
-# file found in their sources. This does not actually update your installed
-# software! For that, keeping reading.
+# apt-get
+# Command-line interface to APT package management
+
+# Update the local database of available packages, as discovered from package
+# index file found in their sources. This does not actually update your
+# installed software! For that, keeping reading.
 apt-get update
 
-# Upgrade installed packages, but there may be exceptions, such as important kernel
-# packages. Also, packages will not be removed, like if they're deprecated, with
-# this method.
+# Upgrade installed packages, but there may be exceptions, such as important
+# kernel packages. Also, packages will not be removed, like if they're
+# deprecated, with this method.
 apt-get upgrade
 
-# Unlike the above, this will upgrade all of the installed packages, and perform
-# other actions required for a successful and thorough upgrade. This will also
-# allow for upgrading to the next minor release of your distributions, such as from
-# Ubuntu '16.04.1' to '16.04.2'.
+# Unlike the above, this will upgrade all of the installed packages, and
+# perform other actions required for a successful and thorough upgrade. This
+# will also allow for upgrading to the next minor release of your
+# distributions, such as from Ubuntu '16.04.1' to '16.04.2'.
 apt-get dist-upgrade
 
 # Clean out (completely) the follow locations of saved DEB files:
@@ -26,22 +29,23 @@ apt-get clean -s
 # View the changelog for the firefox package. Useful prior to or after upgrade.
 apt-get changelog firefox
 
-# Download PKG (one or more) without actually installing or extracting them. A good
-# use for this might be to upgrade an offline system, by downloading the packages
-# on a system using an Internet-able machine. Files are downloaded into the CWD.
+# Download PKG (one or more) without actually installing or extracting them. A
+# good use for this might be to upgrade an offline system, by downloading the
+# packages on a system using an Internet-able machine. Files are downloaded
+# into the CWD.
 apt-get download PKG
 
-# Install PKG (one or more), bringing in dependencies and, provided settings allow
-# it, install recommended and/or suggested packages.
+# Install PKG (one or more), bringing in dependencies and, provided settings
+# allow it, install recommended and/or suggested packages.
 apt-get install PKG
 
-# At times, dependencies won't be installed, yet you still need them; the following
-# command will often fix this, and is usually suggested to the user.
+# At times, dependencies won't be installed, yet you still need them; the
+# following command will often fix this, and is usually suggested to the user.
 apt-get -f install
 
 # Remove PKG, while also purging system-wide configuration files for it.
 apt-get purge PKG
-# Alternative syntax:
+# Alternative syntax to the above.
 apt-get remove --purge PKG
 
 # Often used to first update the local database of packages, then, only if
@@ -50,4 +54,5 @@ apt-get update && apt-get dist-upgrade
 
 # Download specified package (firefox, in this example) and all packages marked
 # thereby as important or dependencies. Files are downloaded into the CWD.
-apt-get download firefox `apt-cache --important depends firefox | awk '{if(NR>1){printf("%s ", $2)}}'`
+apt-get download firefox `apt-cache --important depends firefox |
+    awk '{if(NR>1){printf("%s ", $2)}}'`

sheets/apt-key

@@ -1,2 +1,5 @@
-# List trusted GPG keys for APT.
+# apt-key
+# Command-line APT key management utility
+
+# List APT keys marked as trusted.
 apt-key list

sheets/aspell

@@ -1,3 +1,6 @@
+# aspell
+# Interactive spell-checker for use in a terminal
+
 # Spell check a single file.
 aspell check [FILE]
 

sheets/awk

@@ -1,49 +1,82 @@
-# sum integers from a file or STDIN, one integer per line:
-printf '1\n2\n3\n' | awk '{ sum += $1} END {print sum}'
+# awk
+# Pattern scanning and processing language
 
-# using specific character as separator to sum integers from a file or STDIN
+# Sum integers from a file or STDIN, one integer per line.
+printf '1\n2\n3\n' | awk '{sum += $1} END {print sum}'
+
+# Using specific character as separator to sum integers from a file or STDIN.
 printf '1:2:3' | awk -F ":" '{print $1+$2+$3}'
 
-# print a multiplication table
-seq 9 | sed 'H;g' | awk -v RS='' '{for(i=1;i<=NF;i++)printf("%dx%d=%d%s", i, NR, i*NR, i==NR?"\n":"\t")}'
+# Print a multiplication table.
+awk -v RS='' '
+    {
+        for(i=1;i<=NF;i++){
+            printf("%dx%d=%d%s", i, NR, i*NR, i==NR?"\n":"\t")
+        }
+    }
+' <<< "$(seq 9 | sed 'H;g')"
 
-# Specify output separator character
+# Specify output separator character.
 printf '1 2 3' | awk 'BEGIN {OFS=":"}; {print $1,$2,$3}'
 
-# search for a paragraph containing string
+# Search paragraph for the given REGEX match.
 awk -v RS='' '/42B/' file
 
-# display only first column from multi-column text
-echo "first-column  second-column  third-column" | awk '{print $1}'
+# Display only first field in text taken from STDIN.
+echo 'Field_1  Field_2  Field_3' | awk '{print $1}'
+# Note that in this case, you're far better off using cut(1).
 
 # Use AWK solo; without the need for something via STDIN.
-awk BEGIN'{printf("Example text.\n")}'
+awk 'BEGIN {print("Example text.")}'
 
-# Accessing environment variables from within AWK.
-awk 'BEGIN{print ENVIRON["LS_COLORS"]}'
+# Access environment variables from within AWK.
+awk 'BEGIN {print ENVIRON["LS_COLORS"]}'
 
-# One method to count the number of lines; in this case, read from STDIN.
-free | awk '{i++} END{print i}'
+# Count number of lines taken from STDIN.
+free | awk '{L++} END {print(L)}'
+# Cleaner, more efficient approach to the above.
+free | awk 'END {print(NR)}'
 
 # Output unique list of available sections under which to create a DEB package.
-awk '!A[$1]++{print($1)}' <<< "$(dpkg-query --show -f='${Section}\n')"
+awk '!A[$1]++ {print($1)}' <<< "$(dpkg-query --show -f='${Section}\n')"
 
 # Using process substitution (`<()` is NOT command substitution), with AWK and
 # its associative array variables, we can print just column 2 for lines whose
 # first column is equal to what's between the double-quotes.
-awk '{NR!=1&&A[$1]=$2} END{print(A["Mem:"])}' <(free -h)
+awk '{NR != 1 && A[$1]=$2} END {print(A["Mem:"])}' <(free -h)
 # While below is an easier and simpler solution to the above, it's not at all
 # the same, and in other cases, the above is definitely preferable.
-awk '/^Mem:/{print($2)}' <(free -h)
+awk '/^Mem:/ {print($2)}' <(free -h)
 
 # Output list of unique uppercase-only, sigil-omitted variables used in [FILE].
-awk '{for(F=0; F<NF; F++){if($F~/^\$[A-Z_]+$/){A[$F]++}}} END{for(I in A){X=substr(I, 2, length(I)); printf("%s\n", X)}}' [FILE]
+awk '
+    {
+        for(F=0; F<NF; F++){
+            if($F~/^\$[A-Z_]+$/){
+                A[$F]++
+            }
+        }
+    }
+    END {
+        for(I in A){
+            X=substr(I, 2, length(I))
+            printf("%s\n", X)
+        }
+    }
+' [FILE]
 
 # Output only lines from FILE between PATTERN_1 and PATTERN_2. Good for logs.
-awk '/PATTERN_1/,/PATTERN_2/{print}' [FILE]
+awk '/PATTERN_1/,/PATTERN_2/ {print}' [FILE]
 
 # Pretty-print a table of an overview of the non-system users on the system.
-awk -SPF ':' 'BEGIN {printf("%-17s %-4s %-4s %-s\n", "NAME", "UID", "GID", "SHELL")} $3>=1000 && $1!="nobody" {printf("%-17s %-d %-d %-s\n", $1, $3, $4, $7)}' /etc/passwd
+awk -F ':' '
+    BEGIN {
+        printf("%-17s %-4s %-4s %-s\n", "NAME", "UID", "GID", "SHELL")
+    }
+    $3 >= 1000 && $1 != "nobody" {
+        printf("%-17s %-d %-d %-s\n", $1, $3, $4, $7)
+    }
+' /etc/passwd
 
 # Display the total amount of MiB of RAM available in the machine. This is also
 # a painful but useful workaround to get the units comma-separated, as would be

sheets/aws

@@ -1,38 +1,43 @@
-# install aws cli
+# aws
+# ???
+
+# Install AWS CLI, using a Python package installer. This is available in the
+# Ubuntu 16.04 repositories, so is probably available in other distributions'
+# repositories, therefore I'd recommend using that unless otherwise required.
 pip install awscli
 
-# configure AWS CLI
+# Configure AWS CLI.
 aws configure
 
-# describe instances in the current account
+# Describe instances in the current account.
 aws ec2 describe-instances --instance-ids i-01234567
 
-# list public IP addresses of instances
+# List public IP addresses of instances.
 aws ec2 describe-instances \
   --query "Reservations[*].Instances[*].PublicIpAddress" \
   --output=text
 
-# start instance with the specified id
+# Start instance with the specified ID.
 aws ec2 start-instances --instance-ids i-12345678c
 
-# copy directory to S3
+# Copy directory to S3.
 aws s3 cp ${directory} s3://${bucket}/${directory} --recursive
 
-# sync directory with S3
+# Sync directory with S3.
 aws s3 sync ${directory} s3://${bucket}/${directory} --exclude *.tmp
 
-# list s3 buckets
+# List S3 buckets.
 aws s3 ls
 
-# remove s3 bucket
+# Remove S3 bucket.
 aws s3 rb --force s3://${bucket_name}
 
-# get bucket logging
+# Get bucket logging.
 aws s3api get-bucket-logging --bucket ${bucket_name}
 
-# AWS cloudformation list stacks
+# AWS cloudformation list stacks.
 aws cloudformation list-stacks \
  --stack-status-filter [ CREATE_COMPLETE | UPDATE_COMPLETE | etc.. ]
 
-# other useful commands:
+# Follow the below link for some other useful commands.
 # https://github.com/toddm92/aws/wiki/AWS-CLI-Cheat-Sheet

sheets/az

@@ -62,11 +62,11 @@ az disk list --output table
 
 # Copy blob
 az storage blob copy start \
-	--source-uri 'https://md-ldh5nknx2rkz.blob.core.windows.net/jzwuuuzzapn0/abcd?sv=2017-04-17&sr=b&si=68041718-6828-4f5e-9e6e-a1b719975062&sig=XXX' \
-	--account-key XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX== \
-	--account-name destaccount \
-	--destination-container vms \
-	--destination-blob DESTINATION-blob.vhd
+    --source-uri 'https://md-ldh5nknx2rkz.blob.core.windows.net/jzwuuuzzapn0/abcd?sv=2017-04-17&sr=b&si=68041718-6828-4f5e-9e6e-a1b719975062&sig=XXX' \
+    --account-key XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX== \
+    --account-name destaccount \
+    --destination-container vms \
+    --destination-blob DESTINATION-blob.vhd
 
 # List virtual networks
 az network vnet list --output table

sheets/bash

@@ -6,23 +6,23 @@ done
 # For example:
 for CurDay in Monday Tuesday Wednesday Thursday Friday Saturday Sunday
 do
-	printf "%s\n" "$CurDay"
+    printf "%s\n" "$CurDay"
 done
 
 # To implement a case statement:
 case $1 in
     0)
-		echo "Found a '0'." ;;
+        echo "Found a '0'." ;;
     1)
-		echo "Found a '1'." ;;
+        echo "Found a '1'." ;;
     2)
-		echo "Found a '2'." ;;
+        echo "Found a '2'." ;;
     3*)
-		echo "Something beginning with '3' found." ;;
-	'')
-		echo "Nothing (null) found." ;;
-	*)
-		echo "Anything else found." ;;
+        echo "Something beginning with '3' found." ;;
+    '')
+        echo "Nothing (null) found." ;;
+    *)
+        echo "Anything else found." ;;
 esac
 
 # Turn on built-in Bash debugging output:
@@ -67,8 +67,8 @@ command -v ${program} >/dev/null 2>&1 || error "${program} not installed"
 # However, that is a solution commonly found in a script using the Bourne shell, so
 # in this case, an alternative, Bash-like, and more accurate version could be:
 if ! type -fP bash > /dev/null 2>&1; then
-	printf "ERROR: Dependency 'bash' not met." >&2
-	exit 1
+    printf "ERROR: Dependency 'bash' not met." >&2
+    exit 1
 fi
 
 # Send both STDOUT and STDERR from COMMAND to FILE. The `2>&1` must go at the end.

sheets/fdisk

@@ -47,12 +47,13 @@ UUID=<blkid#> /opt defaults 0 0 # 00 disable disk checking and metadata dumping
 mount -a
 df -h /opt
 
-# Extending a physical disk (vm)
-1.  Unmount drive - comment out /etc/fstab entry for /dev/sdc
-2.  Increase drive physical space
-3.  parted /dev/sdc - 'p' 	#print partitions on /dev/sdc
-4.  fdisk /dev/sdc - 'p' - 'd' - 'n' (defaults) - w	# delete old partition, create new partition
-5.  reboot
-6.  e2fsck -f /dev/sdc1
-7.  resize2fs /dev/sdc1
-8.  mount /dev/sdc1 - uncomment fstab
+# Extending a physical disk (vm). Step 3 prints partitions on `/dev/sdc`. Step
+# 4 deletes the old partition, then creates a new one.
+1. Unmount drive. Comment out `/etc/fstab` entry for `/dev/sdc`.
+2. Increase drive physical space
+3. parted /dev/sdc - 'p'
+4. fdisk /dev/sdc - 'p' - 'd' - 'n' (defaults) - w
+5. reboot
+6. e2fsck -f /dev/sdc1
+7. resize2fs /dev/sdc1
+8. mount /dev/sdc1 - uncomment fstab

sheets/find

@@ -1,61 +1,115 @@
-# Find files by case-insensitive extension (ex: .jpg, .JPG, .jpG):
+# find
+# Search for files in a directory hierarchy
+
+# Find files by case-insensitive extension, such as `.jpg`, `.JPG`, & `.jpG`).
+# By default, find(1) uses glob pathname pattern matching. To avoid shell
+# interpretation, the glob either must be expanded or the string quoted.
 find . -iname '*.jpg'
 
-# Find directories:
+# Find directories.
 find . -type d
 
-# Find files:
+# Find files. Specifically files; not directories, links, FIFOs, etc.
 find . -type f
 
-# Find files by octal permission:
+# Find files set to the provided octal mode (permissions).
 find . -type f -perm 777
 
-# Find files with setuid bit set:
+# Find files with setuid bit set, keeping to the same filesystem.
 find . -xdev \( -perm -4000 \) -type f -print0 | xargs -0 ls -l
-
-# To find files with extension '.txt' and remove them:
-find ./path/ -name '*.txt' -exec rm '{}' \;
-
-# Find files with extension '.txt' and look for a string into them:
+# The above is a useful demonstration of some pitfalls into which a user can
+# fall, where the below is the above but corrected. Here is why:
+#
+#   * The `.` (current working directory) is assumed when no path is provided.
+#   * Group syntax (parentheses) was used, but nothing was actually grouped.
+#   * A lot of people have their ls(1) command aliased in many ways, -
+#     potentially causing problems with the output and how xargs(1) handles it.
+#     By escaping the command, we temporarily override any aliases and even
+#     functions by the same name.
+#   * At least in my experience, the prior xargs(1) is not as reliable.
+#   * The `-print0` and `xargs -0` is great, but unnecessary (except when?).
+#
+# However, it might be more preferred to simply use find(1)'s own `-printf`
+# flag, in order to avoid the need for xargs(1) and ls(1), which should be many
+# times faster, and allows for more specificity.
+find -perm -4000 -type f -print0 | xargs -I '{}' -0 \ls -l '{}'
+
+# Find and remove files with case-senstive extension of `.txt`.
+find [PATH] -name '*.txt' -exec rm '{}' \;
+# The above is much more efficiently written as shown below, as find(1) has its
+# own built-in delete function, not to mention a single rm(1) process was
+# previously executed for each file processed, which is comparatively slow.
+find [PATH] -name '*.txt' -delete
+
+# Find files with extension '.txt' and look for a string into them.
 find ./path/ -name '*.txt' | xargs grep 'string'
 
-# Find files with size bigger than 5 Mb and sort them by size:
+# Find files with size bigger than 5 Mb and sort them by size.
 find . -size +5M -type f -print0 | xargs -0 ls -Ssh | sort -z
 
-# Find files bigger thank 2 MB and list them:
+# Find files bigger thank 2 MB and list them.
 find . -type f -size +20000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'
-
-# Find files modified more than 7 days ago and list file information
+# Alternative, faster approach* to the above.
+#
+# Why it's faster:
+#
+#   * No need for an external process, like ls(1).
+#   * The use of `;` with the `-exec` flag executes an ls(1) process for each
+#     file found, which is comparatively very slow.
+#   * The `printf` feature is built in and special to awk(1).
+#
+# That said, awk(1) or gawk(1) is doing a little more here, in order to get
+# somewhat of a human-readable file size, but its impact is likely negligible.
+find -type f -size +20000k -printf '%s %P\n' |
+    awk "{printf(\"%'dM %s\n\", \$1 / (1024 * 1024), \$2)}"
+
+# Find files modified more than 7 days ago and list file information.
 find . -type f -mtime +7d -ls
 
-# Find symlinks owned by a user and list file information
-find . -type l --user=username -ls
+# Find symlinks owned by the given user, then list file information.
+find -type l -user [NAME] -ls
+# The following may be the syntax used on a Mac, however this is not valid on
+# Linux, or at least version 4.7.0. All flags in GNU find(1) are one `-` only.
+find . -type l --user=[NAME] -ls
 
-# Search for and delete empty directories
+# Search for and delete empty directories.
 find . -type d -empty -exec rmdir {} \;
+# A far more efficient approach to the above. If no path is provided, then the
+# current working directory (CWD) is assumed, making the `.` superfluous.
+find -type d -empty -delete
 
-# Search for directories named build at a max depth of 2 directories
+# Search for directories named `build` at a maximum depth of 2 directories.
+# This means that find will not recursively search beyond two levels.
 find . -maxdepth 2 -name build -type d
 
-# Search all files who are not in .git directory
-find . ! -iwholename '*.git*' -type f
+# Search all files which are not in a `.git` directory. Depending on the shell
+# used, the bang (`!`) may need to be escaped, to avoid shell interpretation.
+# Alternatively, although non-POSIX, the `-not` flag can be used.
+find . \! -iwholename '*.git*' -type f
 
-# Find all files that have the same node (hard link) as MY_FILE_HERE
-find . -type f -samefile MY_FILE_HERE 2>/dev/null
+# Find all files that have the same inode (indicating hard link) as FILE. All
+# output going to STDERR (typically error messages) will also be redirected to
+# `/dev/null`, a special pseudo-file where data is sent to die.
+find . -type f -samefile [FILE] 2>/dev/null
 
-# Find all files in the current directory and modify their permissions
+# Find all files in the current directory and modify their permissions.
 find . -type f -exec chmod 644 {} \;
 
-# Find files with extension '.txt.' and edit all of them with vim
-# vim is started only once for all files
+# Find files with extension `.txt` and edit all of them with vim(1).
+#
+# The use of `+` (escaped to avoid shell interpretation) with `-exec` means
+# that only one process (in this case, `vim`) per `exec`ution is used. If `;`
+# is instead used (would also need escaping), then one `vim` process would be
+# used per file.
 find . -iname '*.txt' -exec vim {} \+
 
-# Find all files with extension '.png' and rename them by changing extension to
-# '.jpg' (base name is preserved)
+# Find files with extension `.png`, then rename their extension to `.jpg`. It's
+# highly important that `\;` is used here, instead of `\+`, otherwise it'd make
+# a right mess of the files, due to the way in which mv(1) works.
 find . -type f -iname '*.png' -exec bash -c 'mv "$0" "${0%.*}.jpg"' {} \;
 
 # Use logic and grouping to delete extension-specific files.
 find \( -iname "*.jpg" -or -iname "*.sfv" -or -iname "*.xspf" \) -type f -delete
 
-# List all executable files, by basename, found within PATH.
+# List executable files, by basename, found within PATH.
 find ${PATH//:/ } -type f -executable -printf "%P\n"

sheets/go

@@ -19,5 +19,5 @@ go install
 # See also:
 #   Go language cheat sheets at /go/
 #   list of pages:      /go/:list
-#   learn go:       	/go/:learn
+#   learn go:           /go/:learn
 #   search in pages:    /go/~keyword

sheets/js

@@ -1,18 +1,19 @@
 # js
 #
-# JavaScript often abbreviated as "JS", is a high-level, dynamic, untyped, interpreted run-time language.
-# It has been standardized in the ECMAScript language specification.
+# JavaScript often abbreviated as "JS", is a high-level, dynamic, untyped, -
+# interpreted run-time language. It has been standardized in the ECMAScript
+# language specification.
 #
-# js is a JavaScript shell, part of SpiderMonkey
-# to install spidermonkey: (in Debian) apt-get install libmozjs-24-bin
+# `js` is a JavaScript shell, part of SpiderMonkey. To install spidermonkey in
+# Debian systems, execute: apt-get install libmozjs-24-bin
 
-# Run the shell in interactive mode
+# Launch an interactive JavaScript session.
 js
 
-# Run the JavaScript code in the file hello.js
+# Run the JavaScript code in the file `hello.js`.
 js hello.js
 
-# Run hello.js then drop into the interactive shell
+# Run the `hello.js` file, then drop into the interactive shell.
 js -f hello.js -i
 
 # See also:

sheets/libreoffice

@@ -1,9 +1,11 @@
-# Convert documents to PDF
+# libreoffice
+# Office productivity suite
+
+# Convert documents to PDF.
 libreoffice --headless --convert-to pdf *.pptx
 
-# Save them to a different directory?
+# Save PDFs to a different directory?
 libreoffice --headless --convert-to pdf *.docx --outdir ~/docs/
 
-# Convert files nested inside folders?
-# This uses sharkdp/fd, you could use GNU find, xargs etc.
+# Convert files nested inside folders? Uses sharkdp/fd, IE: find(1) & xargs(1).
 fd -e doc -e docx -x libreoffice --headless --convert-to pdf --outdir {//} {}

sheets/lua

@@ -1,17 +1,25 @@
 # lua
-# A powerful, light-weight embeddable programming language.
+# Simple, extensible, embeddable programming language
+
+# You may not have access to the `lua` command, but instead to something like
+# `lua5.3` or one of a different version. The following information assumes you
+# have the `lua` command, as-is, but alternative commands may also work the
+# same or similarly, version allowing.
 
 # Start an interactive Lua shell:
 lua
 
-# Execute a Lua script:
-lua script_name.lua --optional-argument
+# Execute a Lua script.
+lua script_name.lua
+# Execute a Lua script, with arguments (IE: flags) given to the script itself.
+lua script_name.lua [ARGS]
 
-# Execute a Lua expression:
-lua -e 'print( "Hello World" )'
+# Execute a Lua expression(s), as though executed from within a script.
+lua -e 'print("Hello World")'
 
-# All options are handled in order, except -i. For instance, an invocation like
-# first set a to 1, then print the value of a (1), and finally run the file script.lua
+# All options are handled in order, except `-i`. For instance, an invocation
+# like first set a to 1, then print the value of a (1), and finally run the
+# file `script.lua`
 lua -e'a=1' -e 'print(a)' script.lua
 
 # See also:

sheets/lynx

@@ -1,10 +1,13 @@
-# Dump $url, do not show links urls
-lynx -dump -nolist $url
+# lynx
+# Classic non-graphical (CLI) web browser
 
-# Use lynx to run repeating website actions
-# For creating your keystroke file, use:
-#   lynx -cmd_log yourfile
-lynx -accept_all_cookies -cmd_script=/your/keystroke-file
+# Dump [URL]; do not show link URLs.
+lynx -dump -nolist [URL]
 
-# convert html to text
+# Creating your keystroke file for use with lynx(1).
+lynx -cmd_log [FILE]
+# Use above keystroke file to run repeating website actions.
+lynx -accept_all_cookies -cmd_script=[FILE]
+
+# Convert HTML from STDIN to text, then dump it to STDOUT.
 lynx -force_html -stdin -dump -nolist

sheets/mutt

@@ -1,80 +1,78 @@
-# Send a mail with a subject, cc, and an attachment
+# mutt
+# Text-based mailreader supporting MIME, GPG, PGP and threading
+
+# Send E-Mail with subject, cc, and attachment.
 mutt -s "Site Backup" -a backup.tar -c user@example.com user2@example.com
 
-# Send a mail with a blind carbon copy (bcc)
+# Send E-Mail with blind carbon copy (bcc).
 mutt -s "hello" -b user2@example.com user@example.com
 
-#
 # Select (tag) messages: shift+t (T)
 #
-  = (string)
-  ~ (expression)
-# 
-  ~b expr     (message with expr in body)
-   [b]body
-   [B]whole message
-   [f]rom
-   [c]c'ed
-   [C]c'ed or to
-   [h]eader
-#  
-  ~m from-to  (range)
-  ~d from-to  (date range)
-# 
-  ~N (new messages)
-  ~U (unread messages)
-  ~R (read messages)
-  ~A (all messages)
-  ~D (deleted messages)
-  ~p (message to you)
-  ~P (message from you)
-  ~= (duplicated messages)
-  ~$ (unref messages)
-# 
-#  Logical operators:
+#  = (string)
+#  ~ (expression)
 #
-    AND = ~P ~N (new messages from you)
-    OR  = ~P | ~N (new messages of messages from you)
-    ()  = (~= ~$) | ~N
+#  ~b expr     (message with expr in body)
+#   [b]body
+#   [B]whole message
+#   [f]rom
+#   [c]c'ed
+#   [C]c'ed or to
+#   [h]eader
 #
-#  
-#  DATES
+#  ~m from-to  (range)
+#  ~d from-to  (date range)
 #
-    DD/MM/YY
-    ~d 20/1/95-31/10/95  (from 20/01/95 to 31/10/95)
-    ~d -31/10/95         (before 31/10/95)
-    ~d 20/1/95-          (after 20/01/95)
-    ~d 20/1/95           (only 20/01/95)
-    ~d 20/1/95*2w        (two weeks around 20/01/95)
-               [w]eek
-               [d]day
-               [m]onth
-               [y]ear
-    can use *(around), +(after) or -(before)
-#   
-    ~d <1m               (messages newer than 1 month)
-    ~d >1y               (messages older than 1 year)
-    ~d =1d               (exact one day)
-
-    
+#  ~N (new messages)
+#  ~U (unread messages)
+#  ~R (read messages)
+#  ~A (all messages)
+#  ~D (deleted messages)
+#  ~p (message to you)
+#  ~P (message from you)
+#  ~= (duplicated messages)
+#  ~$ (unref messages)
 #
-# Keys
+#  Logical operators:
 #
- shift+d (D) : delete messages using pattern
- shift+t (T) : select messages using pattern
- shift+u (U) : undelete messages using pattern
- ctrl+t      : un-selected messages using pattern
+#   AND = ~P ~N (new messages from you)
+#   OR  = ~P | ~N (new messages of messages from you)
+#   ()  = (~= ~$) | ~N
 #
+#  DATES
+#
+#   DD/MM/YY
+#   ~d 20/1/95-31/10/95  (from 20/01/95 to 31/10/95)
+#   ~d -31/10/95         (before 31/10/95)
+#   ~d 20/1/95-          (after 20/01/95)
+#   ~d 20/1/95           (only 20/01/95)
+#   ~d 20/1/95*2w        (two weeks around 20/01/95)
+#               ^
+#              [w]eek
+#              [d]day
+#              [m]onth
+#              [y]ear
+#
+#    Can use `*(around)`, `+(after)` or `-(before)`.
 #
- d           : delete message
- N           : mark as new
- C           : copy message to another folder(mailbox)
- o, O        : change sort, reverse sort
- ctrl+ D, U  : Deleted, Undelete a thread
- ctrl+R      : mark current thread as read
- esc+t       : select thread
- esc+ v, V   : collapse thread, collapse all threads
- w,W         : add, remove flags
+#    ~d <1m               (messages newer than 1 month)
+#    ~d >1y               (messages older than 1 year)
+#    ~d =1d               (exact one day)
+
+
+# Keyboard shortcuts.
 #
-T ~U ;WN ctrl+t .
-mark unread msgs, remove its new flag, unselect them
+# shift+d (D)           : Delete messages using pattern
+# shift+t (T)           : Select messages using pattern
+# shift+u (U)           : Un-delete messages using pattern
+# ctrl+t                : de-selected messages using pattern
+# d                     : Delete message
+# N                     : Mark as new
+# C                     : Copy message to another folder(mailbox)
+# o, O                  : Change sort, reverse sort
+# ctrl+ D, U            : Deleted, Undelete a thread
+# ctrl+R                : Mark current thread as read
+# esc+t                 : Select thread
+# esc+ v, V             : Collapse thread, collapse all threads
+# w,W                   : Add, remove flags
+# T ~U ;WN ctrl+t .     : Mark unread msgs, remove its new flag, de-select them

sheets/nl

@@ -1,7 +1,10 @@
-# Number lines given to `nl` via STDIN.
+# nl
+# Number lines of files
+
+# Number lines given to nl(1) via STDIN.
 printf "Here\nis\nsome\nexample\ntext." | nl
 
-# Number (all) lines given to `nl` via provided file(s).
+# Number (all) lines given to nl(1) via provided file(s).
 nl -b a /path/to/file
-# The above can also be achieved with `cat`, which is perhaps more portable:
+# The above can also be achieved with cat(1), which is perhaps more portable:
 cat -n /path/to/file

sheets/nodejs

@@ -0,0 +1,4 @@
+# nodejs
+# Server-side JavaScript
+
+# Duplicate sheet -- please refer instead to: cheat.sh/js

sheets/xargs

@@ -15,8 +15,8 @@ find -name \*.pdf -type f -print0 | xargs -0rn10 rm
 find -name \*.pdf | xargs -I{} rm -rf '{}'
 
 # Will show every .pdf like:
-#	&toto.pdf=
-#	&titi.pdf=
+#    &toto.pdf=
+#    &titi.pdf=
 # -n1 => One file by one file. ( -n2 => 2 files by 2 files )
 find -name \*.pdf | xargs -I{} -n1 echo '&{}='
 # The above is, however, much faster and easier without xargs:

sheets/xev

@@ -1,14 +1,26 @@
-# Show keycodes used by Xorg
-# start xev and show only the relevant parts:
-xev | awk -F'[ )]+' '/^KeyPress/ { a[NR+2] } NR in a { printf "%-3s %s\n", $5, $8 }'
+# xev
+# Print contents of X events
 
-# Alternative approach to show keycodes, with standard AWK formatting.
+# Start xev(1) and show only the relevant parts.
+xev | awk -F'[ )]+' '
+    /^KeyPress/ {
+        a[NR+2]
+    }
+    NR in a {
+        printf "%-3s %s\n", $5, $8
+    }
+'
+# Alternative approach to showing keycodes.
+#
+# Note that the use of `<(xev)` is process substitution, which is unavailable
+# in the Bourne Shell and its standard derivatives, nor is it available in Bash
+# with its own POSIX mode enabled.
 awk '
-	/^KeyPress/ {
-		A[NR+2]
-	}
-	NR in A {
-		B=substr($7, 0, length($7) - 2)
-		printf("%3d %s\n", $4, B)
-	}
+    /^KeyPress/ {
+        A[NR+2]
+    }
+    NR in A {
+        B=substr($7, 0, length($7) - 2)
+        printf("%3d %s\n", $4, B)
+    }
 ' <(xev)

sheets/xsel

@@ -1,21 +1,20 @@
 # xsel
-#
-# X11 selection and clipboard manipulation tool.
+# Command-line tool to access X clipboard and selection buffers
 
-# Use a command's output as input of the clip[b]oard (equivalent to Ctrl + C):
+# Read from STDIN and save it to the clipboard; as if `Ctrl + C`.
 echo 123 | xsel -ib
-
-# Use the contents of a file as input of the clipboard:
+# A file's contents can also be provided to xsel(1x) via STDIN.
 cat file | xsel -ib
 
-# Output the clipboard's contents into the terminal (equivalent to Ctrl + V):
+# Send the clipboard's contents to STDOUT; as if `Ctrl + V`.
 xsel -ob
-
-# Output the clipboard's contents into a file:
+# The contents of the clipboard can be saved to a file(s). Note that the use of
+# `>` means that any existing file by the same name will be overwritten. Use
+# `>>` to instead append the data to that file.
 xsel -ob > file
 
-# Clear the clipboard:
+# Clear the clipboard.
 xsel -cb
 
-# Output the X11 primary selection's contents into the terminal (equivalent to a mouse middle-click):
+# Send X11 primary selection to STDOUT, as if clicking mouse's middle button.
 xsel -op