Added conditionals

README.md

@@ -93,6 +93,11 @@ See something that is incorrectly described, buggy or outright wrong? Open an is
 * [BRACE EXPANSION](#brace-expansion)
     * [Ranges](#ranges)
     * [String Lists](#string-lists)
+* [CONDITIONAL EXPRESSIONS](#conditional-expressions)
+    * [File Conditionals](#file-conditionals)
+    * [File Comparisons](#file-comparisons)
+    * [Variable Conditionals](#variable-conditionals)
+    * [Variable Comparisons](#variable-comparisons)
 * [ARITHMETIC OPERATORS](#arithmetic-operators)
     * [Assignment](#assignment)
     * [Arithmetic](#arithmetic)
@@ -1197,6 +1202,67 @@ rm -rf ~/Downloads/{Movies,Music,ISOS}
 
 <!-- CHAPTER END -->
 
+
+<!-- CHAPTER START -->
+
+# CONDITIONAL EXPRESSIONS
+
+## File Conditionals
+
+| Expression | Value  | What does it do? |
+| ---------- | ------ | ---------------- |
+| `-a`       | `file` | If file exists.
+| `-b`       | `file` | If file exists and is a block special file.
+| `-c`       | `file` | If file exists and is a character special file.
+| `-d`       | `file` | If file exists and is a directory.
+| `-e`       | `file` | If file exists.
+| `-f`       | `file` | If file exists and is a regular file.
+| `-g`       | `file` | If file exists and its set-group-id bit is set.
+| `-h`       | `file` | If file exists and is a symbolic link.
+| `-k`       | `file` | If file exists and its sticky-bit is set
+| `-p`       | `file` | If file exists and is a named pipe (*FIFO*).
+| `-r`       | `file` | If file exists and is readable.
+| `-s`       | `file` | If file exists and its size is greater than zero.
+| `-t`       | `fd`   | If file descriptor is open and refers to a terminal.
+| `-u`       | `file` | If file exists and its set-user-id bit is set.
+| `-w`       | `file` | If file exists and is writable.
+| `-x`       | `file` | If file exists and is executable.
+| `-G`       | `file` | If file exists and is owned by the effective group ID.
+| `-L`       | `file` | If file exists and is a symbolic link.
+| `-N`       | `file` | If file exists and has been modified since last read.
+| `-O`       | `file` | If file exists and is owned by the effective user ID.
+| `-S`       | `file` | If file exists and is a socket.
+
+## File Comparisons
+
+| Expression | What does it do? |
+| ---------- | ---------------- |
+| `file -ef file2` | If both files refer to the same inode and device numbers.
+| `file -nt file2` | If `file` is newer than `file2` (*uses modification ime*) or `file` exists and `file2` does not.
+| `file -ot file2` | If `file` is older than `file2` (*uses modification ime*) or `file2` exists and `file` does not.
+
+## Variable Conditionals
+
+| Expression | Value | What does it do? |
+| ---------- | ----- | ---------------- |
+| `-o`       | `opt` | If shell option is enabled.
+| `-v`       | `var` | If variable has a value assigned.
+| `-R`       | `var` | If variable is a name reference.
+| `-z`       | `var` | If the length of string is zero.
+| `-n`       | `var` | If the length of string is non-zero.
+
+## Variable Comparisons
+
+| Expression | What does it do? |
+| ---------- | ---------------- |
+| `var = var2` | Equal to.
+| `var == var2` | Equal to (*synonym for `=`*).
+| `var != var2` | Not equal to.
+| `var < var2` | Less than (*in ASCII alphabetical order.*)
+| `var > var2` | Greater than (*in ASCII alphabetical order.*)
+
+<!-- CHAPTER END -->
+
 <!-- CHAPTER START -->
 
 # ARITHMETIC OPERATORS
@@ -1205,7 +1271,7 @@ rm -rf ~/Downloads/{Movies,Music,ISOS}
 
 | Operators | What does it do? |
 | --------- | ---------------- |
-| `=` | Initialize or change the value of a variable.
+| `=`       | Initialize or change the value of a variable.
 
 ## Arithmetic
 
@@ -1585,6 +1651,7 @@ $ get_cursor_pos
 ```sh
 hex_to_rgb() {
     # Usage: hex_to_rgb "#FFFFFF"
+    #        hex_to_rgb "000000"
     : "${1/\#}"
     ((r=16#${_:0:2},g=16#${_:2:2},b=16#${_:4:2}))
     printf '%s\n' "$r $g $b"

manuscript/chapter17.txt

@@ -7,10 +7,8 @@
 ```sh
 hex_to_rgb() {
     # Usage: hex_to_rgb "#FFFFFF"
-    ((r=16#${1:1:2}))
-    ((g=16#${1:3:2}))
-    ((b=16#${1:5:6}))
-
+    : "${1/\#}"
+    ((r=16#${_:0:2},g=16#${_:2:2},b=16#${_:4:2}))
     printf '%s\n' "$r $g $b"
 }
 ```