From 0fc9c1a73e9ebfbbbd9b7e40e2a226d5fb8ff326 Mon Sep 17 00:00:00 2001 From: Paul Buetow Date: Sun, 10 Dec 2023 17:12:14 +0200 Subject: Update content for gemtext --- ...2021-05-16-personal-bash-coding-style-guide.gmi | 64 ++-- gemfeed/atom.xml | 343 ++++++++++++--------- index.gmi | 2 +- uptime-stats.gmi | 2 +- 4 files changed, 241 insertions(+), 170 deletions(-) diff --git a/gemfeed/2021-05-16-personal-bash-coding-style-guide.gmi b/gemfeed/2021-05-16-personal-bash-coding-style-guide.gmi index 4f386850..6831f7e1 100644 --- a/gemfeed/2021-05-16-personal-bash-coding-style-guide.gmi +++ b/gemfeed/2021-05-16-personal-bash-coding-style-guide.gmi @@ -27,13 +27,13 @@ These are my modifications to the Google Guide. Google recommends using always... -``` +```bash #!/bin/bash ``` ... as the shebang line, but that does not work on all Unix and Unix-like operating systems (e.g., the *BSDs don't have Bash installed to /bin/bash). Better is: -``` +```bash #!/usr/bin/env bash ``` @@ -51,7 +51,7 @@ I hit the 80 character line length quicker with the four spaces than with two sp Google recommends breaking up long pipes like this: -``` +```bash # All fits on one line command1 | command2 @@ -64,7 +64,7 @@ command1 \ I think there is a better way like the following, which is less noisy. The pipe | already indicates the Bash that another command is expected, thus making the explicit line breaks with \ obsolete: -``` +```bash # Long commands command1 | command2 | @@ -72,11 +72,13 @@ command1 | command4 ``` +> Update: It's 2023 now, and I have changed my mind. I think Google's way is the better one. It may be a bit more to type, but the leading `|` are a nice eye catcher, so you know immediately what is going on! + ### Quoting your variables Google recommends always quote your variables. Generally, it would be best if you did that only for variables where you are unsure about the content/values of the variables (e.g., content is from an external input source and may contain whitespace or other special characters). In my opinion, the code will become quite noisy when you always quote your variables like this: -``` +```bash greet () { local -r greeting="${1}" local -r name="${2}" @@ -86,7 +88,7 @@ greet () { In this particular example, I agree that you should quote them as you don't know the input (are there, for example, whitespace characters?). But if you are sure that you are only using simple bare words, then I think that the code looks much cleaner when you do this instead: -``` +```bash say_hello_to_paul () { local -r greeting=Hello local -r name=Paul @@ -96,7 +98,7 @@ say_hello_to_paul () { You see, I also omitted the curly braces { } around the variables. I only use the curly braces around variables when it makes the code either easier/clearer to read or if it is necessary to use them: -``` +```bash declare FOO=bar # Curly braces around FOO are necessary echo "foo${FOO}baz" @@ -108,7 +110,7 @@ A few more words on always quoting the variables: For the sake of consistency (a Google recommends using the built-in commands over available external commands where possible: -``` +```bash # Prefer this: addition=$(( X + Y )) substitution="${string/#foo/bar}" @@ -132,7 +134,7 @@ I even didn't get started with what you can do with awk (especially GNU Awk), a Bash does not support a boolean type. I tend just to use the strings 'yes' and 'no' here. I used 0 for false and 1 for true for some time, but I think that the yes/no strings are easier to read. Yes, the Bash script would need to perform string comparisons on every check, but if performance is crucial to you, you wouldn't want to use a Bash script anyway, correct? -``` +```bash declare -r SUGAR_FREE=yes declare -r I_NEED_THE_BUZZ=no @@ -153,14 +155,13 @@ buy_soda $I_NEED_THE_BUZZ Google is in the opinion that eval should be avoided. I think so too. They list these examples in their guide: -``` +```bash # What does this set? # Did it succeed? In part or whole? eval $(set_my_variables) # What happens if one of the returned values has a space in it? variable="$(eval some_function)" - ``` However, if I want to read variables from another file, I don't have to use eval here. I only have to source the file: @@ -195,7 +196,7 @@ The downside is that ShellCheck won't be able to follow the dynamic sourcing any When I do list processing in Bash, I prefer to use pipes. You can chain them through Bash functions as well, which is pretty neat. Usually, my list processing scripts are of a structure like this: -``` +```bash filter_lines () { echo 'Start filtering lines in a fancy way!' >&2 grep ... | sed .... @@ -239,35 +240,38 @@ I often refactor existing Bash code. That leads me to add and removing function The solution is to use of the "assign-then-shift"-method, which goes like this: "local -r var1=$1; shift; local -r var2=$1; shift". The idea is that you only use "$1" to assign function arguments to named (better readable) local function variables. You will never have to bother about "$2" or above. That is very useful when you constantly refactor your code and remove or add function arguments. It's something that I picked up from a colleague (a pure Bash wizard) some time ago: -``` +```bash some_function () { local -r param_foo="$1"; shift local -r param_baz="$1"; shift local -r param_bay="$1"; shift - ... + + # ... } ``` Want to add a param_baz? Just do this: -``` +```bash some_function () { local -r param_foo="$1"; shift local -r param_bar="$1"; shift local -r param_baz="$1"; shift local -r param_bay="$1"; shift - ... + + # ... } ``` Want to remove param_foo? Nothing easier than that: -``` +```bash some_function () { local -r param_bar="$1"; shift local -r param_baz="$1"; shift local -r param_bay="$1"; shift - ... + + # ... } ``` @@ -277,7 +281,7 @@ As you can see, I didn't need to change any other assignments within the functio I call this the paranoid mode. The Bash will stop executing when a command exits with a status not equal to 0: -``` +```bash set -e grep -q foo <<< bar echo Jo @@ -285,14 +289,14 @@ echo Jo Here 'Jo' will never be printed out as the grep didn't find any match. It's unrealistic for most scripts to run in paranoid mode purely, so there must be a way to add exceptions. Critical Bash scripts of mine tend to look like this: -``` +```bash #!/usr/bin/env bash set -e some_function () { - .. some critical code - ... + # .. some critical code + # ... set +e # Grep might fail, but that's OK now @@ -300,11 +304,11 @@ some_function () { local -i ec=$? set -e - .. critical code continues ... + # .. critical code continues ... if [[ $ec -ne 0 ]]; then - ... + : # ... fi - ... + # ... } ``` @@ -316,7 +320,7 @@ There are also a couple of things I've learned from Google's guide. The following looks like a valid Bash code: -``` +```bash if [[ "${my_var}" > 3 ]]; then # True for 4, false for 22. do_something @@ -325,7 +329,7 @@ fi ... but it is probably an unintended lexicographical comparison. A correct way would be: -``` +```bash if (( my_var > 3 )); then do_something fi @@ -333,7 +337,7 @@ fi or -``` +```bash if [[ "${my_var}" -gt 3 ]]; then do_something fi @@ -345,7 +349,7 @@ I have never used the PIPESTATUS variable before. I knew that it's there, but I The PIPESTATUS variable in Bash allows checking of the return code from all parts of a pipe. If it's only necessary to check the success or failure of the whole pipe, then the following is acceptable: -``` +```bash tar -cf - ./* | ( cd "${dir}" && tar -xf - ) if (( PIPESTATUS[0] != 0 || PIPESTATUS[1] != 0 )); then echo "Unable to tar files to ${dir}" >&2 @@ -354,7 +358,7 @@ fi However, as PIPESTATUS will be overwritten as soon as you do any other command, if you need to act differently on errors based on where it happened in the pipe, you'll need to assign PIPESTATUS to another variable immediately after running the command (don't forget that [ is a command and will wipe out PIPESTATUS). -``` +```bash tar -cf - ./* | ( cd "${DIR}" && tar -xf - ) return_codes=( "${PIPESTATUS[@]}" ) if (( return_codes[0] != 0 )); then diff --git a/gemfeed/atom.xml b/gemfeed/atom.xml index 2c16b8bb..0a415179 100644 --- a/gemfeed/atom.xml +++ b/gemfeed/atom.xml @@ -1,6 +1,6 @@ - 2023-12-10T11:46:05+02:00 + 2023-12-10T17:11:56+02:00 foo.zone feed To be in the .zone! @@ -8105,14 +8105,20 @@ assert::equals "$(generate::m
Google recommends using always...

-
-#!/bin/bash 
+
+
#!/bin/bash 
 

 

 ... as the shebang line, but that does not work on all Unix and Unix-like operating systems (e.g., the *BSDs don't have Bash installed to /bin/bash). Better is:

 

-
-#!/usr/bin/env bash
+
+
#!/usr/bin/env bash
 

 

 
Two space soft-tabs indentation


@@ -8129,55 +8135,72 @@ assert::equals "$(generate::m
 

 Google recommends breaking up long pipes like this:

 

-
-# All fits on one line
-command1 | command2
+
+
# All fits on one line
+command1 | command2
 
-# Long commands
-command1 \
-  | command2 \
-  | command3 \
-  | command4
+# Long commands
+command1 \
+  | command2 \
+  | command3 \
+  | command4
 

 

 I think there is a better way like the following, which is less noisy. The pipe | already indicates the Bash that another command is expected, thus making the explicit line breaks with \ obsolete:

 

-
-# Long commands
-command1 |
-    command2 |
-    command3 |
+
+
# Long commands
+command1 |
+    command2 |
+    command3 |
     command4
 

 

+Update: It's 2023 now, and I have changed my mind. I think Google's way is the better one. It may be a bit more to type, but the leading | are a nice eye catcher, so you know immediately what is going on!

+

 
Quoting your variables


 

 Google recommends always quote your variables. Generally, it would be best if you did that only for variables where you are unsure about the content/values of the variables (e.g., content is from an external input source and may contain whitespace or other special characters). In my opinion, the code will become quite noisy when you always quote your variables like this:

 

-
-greet () {
-    local -r greeting="${1}"
-    local -r name="${2}"
-    echo "${greeting} ${name}!"
+
+
greet () {
+    local -r greeting="${1}"
+    local -r name="${2}"
+    echo "${greeting} ${name}!"
 }
 

 

 In this particular example, I agree that you should quote them as you don't know the input (are there, for example, whitespace characters?). But if you are sure that you are only using simple bare words, then I think that the code looks much cleaner when you do this instead:

 

-
-say_hello_to_paul () {
-    local -r greeting=Hello
-    local -r name=Paul
-    echo "$greeting $name!"
+
+
say_hello_to_paul () {
+    local -r greeting=Hello
+    local -r name=Paul
+    echo "$greeting $name!"
 }
 

 

 You see, I also omitted the curly braces { } around the variables. I only use the curly braces around variables when it makes the code either easier/clearer to read or if it is necessary to use them:

 

-
-declare FOO=bar
-# Curly braces around FOO are necessary
-echo "foo${FOO}baz"
+
+
declare FOO=bar
+# Curly braces around FOO are necessary
+echo "foo${FOO}baz"
 

 

 A few more words on always quoting the variables: For the sake of consistency (and for making ShellCheck happy), I am not against quoting everything I encounter. I also think that the larger the Bash script becomes, the more critical it becomes always to quote variables. That's because it will be more likely that you might not remember that some of the functions don't work on values with spaces in them, for example. It's just that I won't quote everything in every small script I write. 

@@ -8186,14 +8209,17 @@ echo "foo${FOO}baz"
 

 Google recommends using the built-in commands over available external commands where possible:

 

-
-# Prefer this:
-addition=$(( X + Y ))
-substitution="${string/#foo/bar}"
+
+
# Prefer this:
+addition=$(( X + Y ))
+substitution="${string/#foo/bar}"
 
-# Instead of this:
-addition="$(expr "${X}" + "${Y}")"
-substitution="$(echo "${string}" | sed -e 's/^foo/bar/')"
+# Instead of this:
+addition="$(expr "${X}" + "${Y}")"
+substitution="$(echo "${string}" | sed -e 's/^foo/bar/')"
 

 

 I can't entirely agree here. The external commands (especially sed) are much more sophisticated and powerful than the built-in Bash versions. Sed can do much more than the Bash can ever do by itself when it comes to text manipulation (the name "sed" stands for streaming editor, after all).

@@ -8210,35 +8236,40 @@ substitution="$(echo "${string}" | sed -e 's/^foo/bar/')"
 

 Bash does not support a boolean type. I tend just to use the strings 'yes' and 'no' here. I used 0 for false and 1 for true for some time, but I think that the yes/no strings are easier to read. Yes, the Bash script would need to perform string comparisons on every check, but if performance is crucial to you, you wouldn't want to use a Bash script anyway, correct?

 

-
-declare -r SUGAR_FREE=yes
-declare -r I_NEED_THE_BUZZ=no
+
+
declare -r SUGAR_FREE=yes
+declare -r I_NEED_THE_BUZZ=no
 
-buy_soda () {
-    local -r sugar_free=$1
+buy_soda () {
+    local -r sugar_free=$1
 
-    if [[ $sugar_free == yes ]]; then
-        echo 'Diet Dr. Pepper'
-    else
-        echo 'Pepsi Coke'
-    fi
+    if [[ $sugar_free == yes ]]; then
+        echo 'Diet Dr. Pepper'
+    else
+        echo 'Pepsi Coke'
+    fi
 }
 
-buy_soda $I_NEED_THE_BUZZ
+buy_soda $I_NEED_THE_BUZZ
 

 

 
Non-evil alternative to variable assignments via eval


 

 Google is in the opinion that eval should be avoided. I think so too. They list these examples in their guide:

 

-
-# What does this set?
-# Did it succeed? In part or whole?
-eval $(set_my_variables)
-
-# What happens if one of the returned values has a space in it?
-variable="$(eval some_function)"
+
+
# What does this set?
+# Did it succeed? In part or whole?
+eval $(set_my_variables)
 
+# What happens if one of the returned values has a space in it?
+variable="$(eval some_function)"
 

 

 However, if I want to read variables from another file, I don't have to use eval here. I only have to source the file:

@@ -8273,36 +8304,39 @@ Hello paul, it is Sat 15 May 19:21:12 BST 2021
 

 When I do list processing in Bash, I prefer to use pipes. You can chain them through Bash functions as well, which is pretty neat. Usually, my list processing scripts are of a structure like this:

 

-
-filter_lines () {
-    echo 'Start filtering lines in a fancy way!' >&2
-    grep ... | sed ....
+
+
filter_lines () {
+    echo 'Start filtering lines in a fancy way!' >&2
+    grep ... | sed ....
 }
 
-process_lines () {
-    echo 'Start processing line by line!' >&2
-    while read -r line; do
-        ... do something and produce a result...
-        echo "$result"
-    done 
+process_lines () {
+    echo 'Start processing line by line!' >&2
+    while read -r line; do
+        ... do something and produce a result...
+        echo "$result"
+    done 
 }
 
-# Do some post-processing of the data
-postprocess_lines () {
-    echo 'Start removing duplicates!' >&2
+# Do some post-processing of the data
+postprocess_lines () {
+    echo 'Start removing duplicates!' >&2
     sort -u
 }
 
-genreate_report () {
-    echo 'My boss wants to have a report!' >&2
-    tee outfile.txt
-    wc -l outfile.txt
+genreate_report () {
+    echo 'My boss wants to have a report!' >&2
+    tee outfile.txt
+    wc -l outfile.txt
 }
 
-main () {
-    filter_lines |
-        process_lines |
-        postprocess_lines |
+main () {
+    filter_lines |
+        process_lines |
+        postprocess_lines |
         generate_report
 }
 
@@ -8317,35 +8351,47 @@ main
 

 The solution is to use of the "assign-then-shift"-method, which goes like this: "local -r var1=$1; shift; local -r var2=$1; shift". The idea is that you only use "$1" to assign function arguments to named (better readable) local function variables. You will never have to bother about "$2" or above. That is very useful when you constantly refactor your code and remove or add function arguments. It's something that I picked up from a colleague (a pure Bash wizard) some time ago:

 

-
-some_function () {
-    local -r param_foo="$1"; shift
-    local -r param_baz="$1"; shift
-    local -r param_bay="$1"; shift
-    ...
+
+
some_function () {
+    local -r param_foo="$1"; shift
+    local -r param_baz="$1"; shift
+    local -r param_bay="$1"; shift
+
+    # ...
 }
 

 

 Want to add a param_baz? Just do this:

 

-
-some_function () {
-    local -r param_foo="$1"; shift
-    local -r param_bar="$1"; shift
-    local -r param_baz="$1"; shift
-    local -r param_bay="$1"; shift
-    ...
+
+
some_function () {
+    local -r param_foo="$1"; shift
+    local -r param_bar="$1"; shift
+    local -r param_baz="$1"; shift
+    local -r param_bay="$1"; shift
+
+    # ...
 }
 

 

 Want to remove param_foo? Nothing easier than that:

 

-
-some_function () {
-    local -r param_bar="$1"; shift
-    local -r param_baz="$1"; shift
-    local -r param_bay="$1"; shift
-    ...
+
+
some_function () {
+    local -r param_bar="$1"; shift
+    local -r param_baz="$1"; shift
+    local -r param_bay="$1"; shift
+    
+    # ...
 }
 

 

@@ -8355,34 +8401,40 @@ some_function () {
 

 I call this the paranoid mode. The Bash will stop executing when a command exits with a status not equal to 0:

 

-
-set -e
-grep -q foo <<< bar
+
+
set -e
+grep -q foo <<< bar
 echo Jo
 

 

 Here 'Jo' will never be printed out as the grep didn't find any match. It's unrealistic for most scripts to run in paranoid mode purely, so there must be a way to add exceptions. Critical Bash scripts of mine tend to look like this:

 

-
-#!/usr/bin/env bash
+
+
#!/usr/bin/env bash
 
-set -e
+set -e
 
-some_function () {
-    .. some critical code
-    ...
+some_function () {
+    # .. some critical code
+    # ...
 
-    set +e
-    # Grep might fail, but that's OK now
-    grep ....
-    local -i ec=$?
-    set -e
+    set +e
+    # Grep might fail, but that's OK now
+    grep ....
+    local -i ec=$?
+    set -e
 
-    .. critical code continues ...
-    if [[ $ec -ne 0 ]]; then
-        ...
-    fi
-    ...
+    # .. critical code continues ...
+    if [[ $ec -ne 0 ]]; then
+        : # ...
+    fi
+    # ...
 }
 

 

@@ -8394,27 +8446,36 @@ some_function () {
 

 The following looks like a valid Bash code:

 

-
-if [[ "${my_var}" > 3 ]]; then
-    # True for 4, false for 22.
+
+
if [[ "${my_var}" > 3 ]]; then
+    # True for 4, false for 22.
     do_something
-fi
+fi
 

 

 ... but it is probably an unintended lexicographical comparison. A correct way would be:

 

-
-if (( my_var > 3 )); then
+
+
if (( my_var > 3 )); then
     do_something
-fi
+fi
 

 

 or

 

-
-if [[ "${my_var}" -gt 3 ]]; then
+
+
if [[ "${my_var}" -gt 3 ]]; then
     do_something
-fi
+fi
 

 

 
PIPESTATUS


@@ -8423,24 +8484,30 @@ fi
 

 The PIPESTATUS variable in Bash allows checking of the return code from all parts of a pipe. If it's only necessary to check the success or failure of the whole pipe, then the following is acceptable:

 

-
-tar -cf - ./* | ( cd "${dir}" && tar -xf - )
-if (( PIPESTATUS[0] != 0 || PIPESTATUS[1] != 0 )); then
-    echo "Unable to tar files to ${dir}" >&2
-fi
+
+
tar -cf - ./* | ( cd "${dir}" && tar -xf - )
+if (( PIPESTATUS[0] != 0 || PIPESTATUS[1] != 0 )); then
+    echo "Unable to tar files to ${dir}" >&2
+fi
 

 

 However, as PIPESTATUS will be overwritten as soon as you do any other command, if you need to act differently on errors based on where it happened in the pipe, you'll need to assign PIPESTATUS to another variable immediately after running the command (don't forget that [ is a command and will wipe out PIPESTATUS).

 

-
-tar -cf - ./* | ( cd "${DIR}" && tar -xf - )
-return_codes=( "${PIPESTATUS[@]}" )
-if (( return_codes[0] != 0 )); then
+
+
tar -cf - ./* | ( cd "${DIR}" && tar -xf - )
+return_codes=( "${PIPESTATUS[@]}" )
+if (( return_codes[0] != 0 )); then
     do_something
-fi
-if (( return_codes[1] != 0 )); then
+fi
+if (( return_codes[1] != 0 )); then
     do_something_else
-fi
+fi
 

 

 
Use common sense and BE CONSISTENT.


diff --git a/index.gmi b/index.gmi
index c4c1d1f7..8b0329af 100644
--- a/index.gmi
+++ b/index.gmi
@@ -1,6 +1,6 @@
 # foo.zone
 
-> This site was generated at 2023-12-10T11:46:05+02:00 by `Gemtexter`
+> This site was generated at 2023-12-10T17:11:56+02:00 by `Gemtexter`
 
 ```
    |\---/|
diff --git a/uptime-stats.gmi b/uptime-stats.gmi
index 51ed9fd3..1fb5c186 100644
--- a/uptime-stats.gmi
+++ b/uptime-stats.gmi
@@ -1,6 +1,6 @@
 # My machine uptime stats
 
-> This site was last updated at 2023-12-10T11:46:05+02:00
+> This site was last updated at 2023-12-10T17:11:56+02:00
 
 The following stats were collected via `uptimed` on all of my personal computers over many years and the output was generated by `guprecords`, the global uptime records stats analyser of mine.
 
-- 
cgit v1.2.3