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Shell Programming and Scripting
Is Rule 7 of POSIX shell grammar rules written correctly?
Post 302978852 by Mark_Galeck on Thursday 4th of August 2016 06:25:12 PM
08-04-2016
Is Rule 7 of POSIX shell grammar rules written correctly?
The POSIX shell standard grammar rules are at
Shell Command Language
I am trying to understand Rule 7 and I don't. I think there may be some mistakes there. I am not complaining about the standard; rather, I am concerned that my perception is wrong, and I don't understand something important.
Here are my questions. Please tell me for each question, if the standard is simply written incorrectly, or what is it that I don't understand.
1. Rule 7 is only referenced with yacc symbols cmd_name and cmd_word, not with any symbols that have to do with assignments, yet it is labeled "Assignment preceding command name". Is that a misleading label ?
2. Rule 7a for the first word, in some cases refers to Rule 7b, which is labeled "not the first word". Is that a misleading label ?
3. The yacc symbol cmd_word refers to rule 7b, which says, if the word contains '=' after its first character, then it is an assignment - and not anything to do with a command. Should rule 7b simply state that it is not allowed to have '=' after the first character?
4. Rule 7a is only referenced during parsing simple commands, which cannot have any reserved words in them. Yet Rule 7a in some cases refers to Rule 1, which differentiates between a reserved word and ordinary word.
If there is no possibility of having a reserved word in Rule 7a, there would be no point to refer to any additional Rule 1 at all. Then, there would be no point in having a separate Rule 7a at all. That is because, if the word did not contain '=', Rule 7b says nothing, so we have WORD, and if it did contain '=', then 7b applies. Thus we would only need 7b. Then also, there would be no need for cmd_name symbol, we could just have cmd_word.
Is Rule 7a and cmd_name symbol needed?
Shell Command Language
I am trying to understand Rule 7 and I don't. I think there may be some mistakes there. I am not complaining about the standard; rather, I am concerned that my perception is wrong, and I don't understand something important.
Here are my questions. Please tell me for each question, if the standard is simply written incorrectly, or what is it that I don't understand.
1. Rule 7 is only referenced with yacc symbols cmd_name and cmd_word, not with any symbols that have to do with assignments, yet it is labeled "Assignment preceding command name". Is that a misleading label ?
2. Rule 7a for the first word, in some cases refers to Rule 7b, which is labeled "not the first word". Is that a misleading label ?
3. The yacc symbol cmd_word refers to rule 7b, which says, if the word contains '=' after its first character, then it is an assignment - and not anything to do with a command. Should rule 7b simply state that it is not allowed to have '=' after the first character?
4. Rule 7a is only referenced during parsing simple commands, which cannot have any reserved words in them. Yet Rule 7a in some cases refers to Rule 1, which differentiates between a reserved word and ordinary word.
If there is no possibility of having a reserved word in Rule 7a, there would be no point to refer to any additional Rule 1 at all. Then, there would be no point in having a separate Rule 7a at all. That is because, if the word did not contain '=', Rule 7b says nothing, so we have WORD, and if it did contain '=', then 7b applies. Thus we would only need 7b. Then also, there would be no need for cmd_name symbol, we could just have cmd_word.
Is Rule 7a and cmd_name symbol needed?
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LEARN ABOUT OSX
platform::shell
platform::shell(n) Tcl Bundled Packages platform::shell(n) __________________________________________________________________________________________________________________________________________________ NAME
platform::shell - System identification support code and utilities SYNOPSIS
package require platform::shell ?1.1.4? platform::shell::generic shell platform::shell::identify shell platform::shell::platform shell _________________________________________________________________ DESCRIPTION
The platform::shell package provides several utility commands useful for the identification of the architecture of a specific Tcl shell. This package allows the identification of the architecture of a specific Tcl shell different from the shell running the package. The only requirement is that the other shell (identified by its path), is actually executable on the current machine. While for most platform this means that the architecture of the interrogated shell is identical to the architecture of the running shell this is not generally true. A counter example are all platforms which have 32 and 64 bit variants and where a 64bit system is able to run 32bit code. For these running and interrogated shell may have different 32/64 bit settings and thus different identifiers. For applications like a code repository it is important to identify the architecture of the shell which will actually run the installed packages, versus the architecture of the shell running the repository software. COMMANDS
platform::shell::identify shell This command does the same identification as platform::identify, for the specified Tcl shell, in contrast to the running shell. platform::shell::generic shell This command does the same identification as platform::generic, for the specified Tcl shell, in contrast to the running shell. platform::shell::platform shell This command returns the contents of tcl_platform(platform) for the specified Tcl shell. KEYWORDS
operating system, cpu architecture, platform, architecture platform::shell 1.1.4 platform::shell(n)