Numerous spelling / grammar corrections from Larry Doolittle
<ldoolitt@recycle.lbl.gov>, as well as a few additions / clarifications.
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@ -21,11 +21,12 @@ Declaration Order
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Here is the order in which code should be laid out in a file:
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Here is the order in which code should be laid out in a file:
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- commented program name and one-line description
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- commented author name and email address(es)
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- commented author name and email address(es)
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- commented GPL boilerplate
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- commented GPL boilerplate
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- commented description of program
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- commented longer description / notes for the program (if needed)
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- #includes and #defines
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- #includes and #defines
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- const and globals variables
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- const and global variables
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- function declarations (if necessary)
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- function declarations (if necessary)
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- function implementations
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- function implementations
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@ -37,7 +38,7 @@ This is everybody's favorite flame topic so let's get it out of the way right
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up front.
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up front.
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Tabs vs Spaces in Line Indentation
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Tabs vs. Spaces in Line Indentation
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The preference in Busybox is to indent lines with tabs. Do not indent lines
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The preference in Busybox is to indent lines with tabs. Do not indent lines
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@ -56,7 +57,7 @@ multi-line comments that use an asterisk at the beginning of each line, i.e.:
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Furthermore, The preference is that tabs be set to display at four spaces
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Furthermore, The preference is that tabs be set to display at four spaces
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wide, but the beauty of using only tabs (and not spaces) at the beginning of
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wide, but the beauty of using only tabs (and not spaces) at the beginning of
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lines is that you can set your editor to display tabs at *watever* number of
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lines is that you can set your editor to display tabs at *whatever* number of
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spaces is desired and the code will still look fine.
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spaces is desired and the code will still look fine.
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@ -76,7 +77,7 @@ Put spaces between terms and operators. Example:
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While it extends the line a bit longer, the spaced version is more
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While it extends the line a bit longer, the spaced version is more
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readable. An allowable exception to this rule is the situation where
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readable. An allowable exception to this rule is the situation where
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excluding the spacing makes it more obvious that we are dealing with a
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excluding the spacing makes it more obvious that we are dealing with a
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single term (even if it is a compund term) such as:
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single term (even if it is a compound term) such as:
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if (str[idx] == '/' && str[idx-1] != '\\')
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if (str[idx] == '/' && str[idx-1] != '\\')
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@ -89,12 +90,20 @@ Bracket Spacing
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~~~~~~~~~~~~~~~
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~~~~~~~~~~~~~~~
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If an opening bracket starts a function, it should be on the
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If an opening bracket starts a function, it should be on the
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next line with no spacing before it. However, if a bracet follows an opening
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next line with no spacing before it. However, if a bracket follows an opening
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control block, it should be on the same line with a single space (not a tab)
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control block, it should be on the same line with a single space (not a tab)
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between it and the opening control block statment. Examples:
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between it and the opening control block statement. Examples:
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Don't do this:
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Don't do this:
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while (!done)
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{
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do
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{
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Don't do this either:
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while (!done){
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while (!done){
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do{
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do{
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@ -121,7 +130,7 @@ is being declared or called). Examples:
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while (foo) {
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while (foo) {
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for (i = 0; i < n; i++) {
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for (i = 0; i < n; i++) {
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Do functions like this:
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But do functions like this:
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static int my_func(int foo, char bar)
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static int my_func(int foo, char bar)
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...
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...
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@ -131,8 +140,8 @@ is being declared or called). Examples:
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Cuddled Elses
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Cuddled Elses
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~~~~~~~~~~~~~
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~~~~~~~~~~~~~
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Also, please "cuddle" your else statments by putting the else keyword on the
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Also, please "cuddle" your else statements by putting the else keyword on the
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same line after the right bracket that closes an 'if' statment.
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same line after the right bracket that closes an 'if' statement.
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Don't do this:
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Don't do this:
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@ -151,25 +160,36 @@ same line after the right bracket that closes an 'if' statment.
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stmt;
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stmt;
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}
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}
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The exception to this rule is if you want to include a comment before the else
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block. Example:
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if (foo) {
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stmts...
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}
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/* otherwise, we're just kidding ourselves, so re-frob the input */
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else {
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other_stmts...
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}
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Variable and Function Names
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Variable and Function Names
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---------------------------
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---------------------------
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Use the K&R style with names in all lower-case and underscores occasionally
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Use the K&R style with names in all lower-case and underscores occasionally
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used to seperate words (e.g. "variable_name" and "numchars" are both
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used to separate words (e.g., "variable_name" and "numchars" are both
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acceptable). Using underscores makes variable and function names more readable
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acceptable). Using underscores makes variable and function names more readable
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because it looks like whitespace; using lower-case is easy on the eyes.
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because it looks like whitespace; using lower-case is easy on the eyes.
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Note: The Busybox codebase is very much a mixture of code gathered from a
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Note: The Busybox codebase is very much a mixture of code gathered from a
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variety of locations. This explains why the current codebase contains such a
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variety of sources. This explains why the current codebase contains such a
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plethora of different naming styles (Java, Pascal, K&R, just-plain-weird,
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hodge-podge of different naming styles (Java, Pascal, K&R, just-plain-weird,
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etc.). The K&R guideline explained above should therefore be used on new files
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etc.). The K&R guideline explained above should therefore be used on new files
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that are added to the repository. Furthermore, the maintainer of an existing
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that are added to the repository. Furthermore, the maintainer of an existing
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file that uses alternate naming conventions should -- at his own convenience
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file that uses alternate naming conventions should -- at his own convenience --
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-- convert those names over to K&R style; converting variable names is a very
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convert those names over to K&R style; converting variable names is a very low
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low priority task. Perhaps in the future we will include some magical Perl
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priority task. Perhaps in the future we will include some magical Perl script
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script that can go through and convert files--left as an exersize to the
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that can go through and convert files -- left as an exercise to the reader for
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reader.
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now.
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Tip and Pointers
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Tip and Pointers
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@ -177,31 +197,34 @@ Tip and Pointers
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The following are simple coding guidelines that should be followed:
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The following are simple coding guidelines that should be followed:
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- When in doubt about the propper behavior of a busybox program (output,
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- When in doubt about the proper behavior of a Busybox program (output,
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formatting, options, etc.), model it after the equivalent GNU program.
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formatting, options, etc.), model it after the equivalent GNU program.
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Doesn't matter how that program behaves on some other flavor of *NIX;
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Doesn't matter how that program behaves on some other flavor of *NIX;
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doesn't matter what the POSIX standard says or doesn't say, just model
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doesn't matter what the POSIX standard says or doesn't say, just model
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busybox programs after their GNU counterparts and nobody has to get hurt.
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Busybox programs after their GNU counterparts and nobody has to get hurt.
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- Don't use a '#define var 80' when you can use 'static const int var 80'
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- Don't use a '#define var 80' when you can use 'static const int var 80'
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instead. This makes the compiler do typechecking for you (rather than
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instead. This makes the compiler do type checking for you (rather than
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relying on the more error-prone preprocessor) and it makes debugging
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relying on the more error-prone preprocessor) and it makes debugging
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programs much easier since the value of the variable can be easily queried.
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programs much easier since the value of the variable can be easily
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displayed.
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- If a const variable is used in only one function, do not make it global to
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- If a const variable is used in only one function, do not make it global to
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the file. Instead, declare it inside the function body.
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the file. Instead, declare it inside the function body.
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- Inside applet files, all functions should be declared static so as to keep
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- Inside applet files, all functions should be declared static so as to keep
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the global namespace clean. The only exception to this rule is the
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the global name space clean. The only exception to this rule is the
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"applet_main" function which must be declared extern.
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"applet_main" function which must be declared extern.
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- If you write a function that performs a task that could be useful outside
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- If you write a function that performs a task that could be useful outside
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the immediate file, turn it into a general-purpose function with no ties to
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the immediate file, turn it into a general-purpose function with no ties to
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any applet and put it in the utility.c file instead.
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any applet and put it in the utility.c file instead.
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- Put all help/usage messages in usage.c. Put other strings in messages.c
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- Put all help/usage messages in usage.c. Put other strings in messages.c.
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(Side Note: we might want to use a single file instead of two, food for
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Putting these strings into their own file is a calculated decision designed
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thought).
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to confine spelling errors to a single place and aid internationalization
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efforts, if needed. (Side Note: we might want to use a single file instead
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of two, food for thought).
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- There's a right way and a wrong way to test for sting equivalence with
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- There's a right way and a wrong way to test for sting equivalence with
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strcmp:
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strcmp:
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@ -218,7 +241,9 @@ The following are simple coding guidelines that should be followed:
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The use of the "equals" (==) operator in the latter example makes it much
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The use of the "equals" (==) operator in the latter example makes it much
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more obvious that you are testing for equivalence. The former example with
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more obvious that you are testing for equivalence. The former example with
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the "not" (!) operator makes it look like you are testing for an error.
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the "not" (!) operator makes it look like you are testing for an error. In
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a more perfect world, we would have a streq() function in the string
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library, but that ain't the world we're living in.
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- Do not use old-style function declarations that declare variable types
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- Do not use old-style function declarations that declare variable types
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between the parameter list and opening bracket. Example:
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between the parameter list and opening bracket. Example:
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