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Miscellaneous improvements

This commit is contained in:
Crestwave 2019-01-19 17:20:13 +08:00
parent 2b558f2962
commit 2414ae9f42
9 changed files with 78 additions and 50 deletions
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64
README.md
View File

@ -274,7 +274,7 @@ $ regex "red" '^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'
```shell
is_hex_color() {
if [[ "$1" =~ ^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$ ]]; then
if [[ $1 =~ ^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$ ]]; then
printf '%s\n' "${BASH_REMATCH[1]}"
else
printf '%s\n' "error: $1 is an invalid color."
@ -487,17 +487,17 @@ The Quick Brown
**Using a test:**
```shell
if [[ "$var" == *sub_string* ]]; then
if [[ $var == *sub_string* ]]; then
printf '%s\n' "sub_string is in var."
fi
# Inverse (substring not in string).
if [[ "$var" != *sub_string* ]]; then
if [[ $var != *sub_string* ]]; then
printf '%s\n' "sub_string is not in var."
fi
# This works for arrays too!
if [[ "${arr[*]}" == *sub_string* ]]; then
if [[ ${arr[*]} == *sub_string* ]]; then
printf '%s\n' "sub_string is in array."
fi
```
@ -523,12 +523,12 @@ esac
## Check if string starts with sub-string
```shell
if [[ "$var" == sub_string* ]]; then
if [[ $var == sub_string* ]]; then
printf '%s\n' "var starts with sub_string."
fi
# Inverse (var does not start with sub_string).
if [[ "$var" != sub_string* ]]; then
if [[ $var != sub_string* ]]; then
printf '%s\n' "var does not start with sub_string."
fi
```
@ -536,12 +536,12 @@ fi
## Check if string ends with sub-string
```shell
if [[ "$var" == *sub_string ]]; then
if [[ $var == *sub_string ]]; then
printf '%s\n' "var ends with sub_string."
fi
# Inverse (var does not end with sub_string).
if [[ "$var" != *sub_string ]]; then
if [[ $var != *sub_string ]]; then
printf '%s\n' "var does not end with sub_string."
fi
```
@ -600,7 +600,7 @@ remove_array_dups() {
declare -A tmp_array
for i in "$@"; do
[[ "$i" ]] && IFS=" " tmp_array["${i:- }"]=1
[[ $i ]] && IFS=" " tmp_array["${i:- }"]=1
done
printf '%s\n' "${!tmp_array[@]}"
@ -723,12 +723,12 @@ arr=(apples oranges tomatoes)
# Elements and index.
for i in "${!arr[@]}"; do
printf '%s\n' "${arr[$i]}"
printf '%s\n' "${arr[i]}"
done
# Alternative method.
for ((i=0;i<${#arr[@]};i++)); do
printf '%s\n' "${arr[$i]}"
printf '%s\n' "${arr[i]}"
done
```
@ -945,11 +945,11 @@ printf '' >file
extract() {
# Usage: extract file "opening marker" "closing marker"
while IFS=$'\n' read -r line; do
[[ "$extract" && "$line" != "$3" ]] && \
[[ $extract && $line != "$3" ]] &&
printf '%s\n' "$line"
[[ "$line" == "$2" ]] && extract=1
[[ "$line" == "$3" ]] && extract=
[[ $line == "$2" ]] && extract=1
[[ $line == "$3" ]] && extract=
done < "$1"
}
```
@ -1022,14 +1022,28 @@ Downloads
## Assign and access a variable using a variable
```shell
hello_world="test"
$ hello_world="value"
# Create the variable name.
var1="world"
var2="hello_${var1}"
$ var="world"
$ ref="hello_$var"
# Print the value of the variable name stored in 'hello_$var1'.
printf '%s\n' "${!var2}"
# Print the value of the variable name stored in 'hello_$var'.
$ printf '%s\n' "${!ref}"
value
```
Alternatively, on `bash` 4.3+:
```shell
$ hello_world="value"
$ var="world"
# Declare a nameref.
$ declare -n ref=hello_$var
$ printf '%s\n' "$ref"
value
```
<!-- CHAPTER END -->
@ -1101,7 +1115,7 @@ Contrary to popular belief, there is no issue in utilizing raw escape sequences.
| --------- | ---------------- |
| `${!VAR}` | Access a variable based on the value of `VAR`.
| `${!VAR*}` | Expand to `IFS` separated list of variable names starting with `VAR`. |
| `${!VAR@}` | Expand to `IFS` separated list of variable names starting with `VAR`. |
| `${!VAR@}` | Expand to `IFS` separated list of variable names starting with `VAR`. If double-quoted, each variable name expands to a separate word. |
## Replacement
@ -1741,16 +1755,16 @@ f()for i in "$@"; do echo "$i"; done
```shell
# One line
# Note: The 3rd statement may run when the 1st is true
[[ "$var" == hello ]] && echo hi || echo bye
[[ "$var" == hello ]] && { echo hi; echo there; } || echo bye
[[ $var == hello ]] && echo hi || echo bye
[[ $var == hello ]] && { echo hi; echo there; } || echo bye
# Multi line (no else, single statement)
# Note: The exit status may not be the same as with an if statement
[[ "$var" == hello ]] && \
[[ $var == hello ]] &&
echo hi
# Multi line (no else)
[[ "$var" == hello ]] && {
[[ $var == hello ]] && {
echo hi
# ...
}
@ -1882,7 +1896,7 @@ Fri 15 Jun - 10:00 AM
```shell
$ : \\u
# Expand the parameter as if it were a prompt string
# Expand the parameter as if it were a prompt string.
$ printf '%s\n' "${_@P}"
black
```

16
manuscript/chapter1.txt
View File

@ -100,7 +100,7 @@ $ regex "red" '^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'
```shell
is_hex_color() {
if [[ "$1" =~ ^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$ ]]; then
if [[ $1 =~ ^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$ ]]; then
printf '%s\n' "${BASH_REMATCH[1]}"
else
printf '%s\n' "error: $1 is an invalid color."
@ -313,17 +313,17 @@ The Quick Brown
**Using a test:**
```shell
if [[ "$var" == *sub_string* ]]; then
if [[ $var == *sub_string* ]]; then
printf '%s\n' "sub_string is in var."
fi
# Inverse (substring not in string).
if [[ "$var" != *sub_string* ]]; then
if [[ $var != *sub_string* ]]; then
printf '%s\n' "sub_string is not in var."
fi
# This works for arrays too!
if [[ "${arr[*]}" == *sub_string* ]]; then
if [[ ${arr[*]} == *sub_string* ]]; then
printf '%s\n' "sub_string is in array."
fi
```
@ -349,12 +349,12 @@ esac
## Check if string starts with sub-string
```shell
if [[ "$var" == sub_string* ]]; then
if [[ $var == sub_string* ]]; then
printf '%s\n' "var starts with sub_string."
fi
# Inverse (var does not start with sub_string).
if [[ "$var" != sub_string* ]]; then
if [[ $var != sub_string* ]]; then
printf '%s\n' "var does not start with sub_string."
fi
```
@ -362,12 +362,12 @@ fi
## Check if string ends with sub-string
```shell
if [[ "$var" == *sub_string ]]; then
if [[ $var == *sub_string ]]; then
printf '%s\n' "var ends with sub_string."
fi
# Inverse (var does not end with sub_string).
if [[ "$var" != *sub_string ]]; then
if [[ $var != *sub_string ]]; then
printf '%s\n' "var does not end with sub_string."
fi
```

8
manuscript/chapter18.txt
View File

@ -95,16 +95,16 @@ f()for i in "$@"; do echo "$i"; done
```shell
# One line
# Note: The 3rd statement may run when the 1st is true
[[ "$var" == hello ]] && echo hi || echo bye
[[ "$var" == hello ]] && { echo hi; echo there; } || echo bye
[[ $var == hello ]] && echo hi || echo bye
[[ $var == hello ]] && { echo hi; echo there; } || echo bye
# Multi line (no else, single statement)
# Note: The exit status may not be the same as with an if statement
[[ "$var" == hello ]] && \
[[ $var == hello ]] &&
echo hi
# Multi line (no else)
[[ "$var" == hello ]] && {
[[ $var == hello ]] && {
echo hi
# ...
}

2
manuscript/chapter19.txt
View File

@ -88,7 +88,7 @@ Fri 15 Jun - 10:00 AM
```shell
$ : \\u
# Expand the parameter as if it were a prompt string
# Expand the parameter as if it were a prompt string.
$ printf '%s\n' "${_@P}"
black
```

2
manuscript/chapter2.txt
View File

@ -49,7 +49,7 @@ remove_array_dups() {
declare -A tmp_array
for i in "$@"; do
[[ "$i" ]] && IFS=" " tmp_array["${i:- }"]=1
[[ $i ]] && IFS=" " tmp_array["${i:- }"]=1
done
printf '%s\n' "${!tmp_array[@]}"

4
manuscript/chapter3.txt
View File

@ -41,12 +41,12 @@ arr=(apples oranges tomatoes)
# Elements and index.
for i in "${!arr[@]}"; do
printf '%s\n' "${arr[$i]}"
printf '%s\n' "${arr[i]}"
done
# Alternative method.
for ((i=0;i<${#arr[@]};i++)); do
printf '%s\n' "${arr[$i]}"
printf '%s\n' "${arr[i]}"
done
```

6
manuscript/chapter4.txt
View File

@ -167,11 +167,11 @@ printf '' >file
extract() {
# Usage: extract file "opening marker" "closing marker"
while IFS=$'\n' read -r line; do
[[ "$extract" && "$line" != "$3" ]] && \
[[ $extract && $line != "$3" ]] &&
printf '%s\n' "$line"
[[ "$line" == "$2" ]] && extract=1
[[ "$line" == "$3" ]] && extract=
[[ $line == "$2" ]] && extract=1
[[ $line == "$3" ]] && extract=
done < "$1"
}
```

24
manuscript/chapter6.txt
View File

@ -3,14 +3,28 @@
## Assign and access a variable using a variable
```shell
hello_world="test"
$ hello_world="value"
# Create the variable name.
var1="world"
var2="hello_${var1}"
$ var="world"
$ ref="hello_$var"
# Print the value of the variable name stored in 'hello_$var1'.
printf '%s\n' "${!var2}"
# Print the value of the variable name stored in 'hello_$var'.
$ printf '%s\n' "${!ref}"
value
```
Alternatively, on `bash` 4.3+:
```shell
$ hello_world="value"
$ var="world"
# Declare a nameref.
$ declare -n ref=hello_$var
$ printf '%s\n' "$ref"
value
```
<!-- CHAPTER END -->

2
manuscript/chapter8.txt
View File

@ -6,7 +6,7 @@
| --------- | ---------------- |
| `${!VAR}` | Access a variable based on the value of `VAR`.
| `${!VAR*}` | Expand to `IFS` separated list of variable names starting with `VAR`. |
| `${!VAR@}` | Expand to `IFS` separated list of variable names starting with `VAR`. |
| `${!VAR@}` | Expand to `IFS` separated list of variable names starting with `VAR`. If double-quoted, each variable name expands to a separate word. |
## Replacement