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Top Forums UNIX for Advanced & Expert Users [Discussion] POSIX, the Love of Backticks and All That Jazz Post 302990516 by bakunin on Friday 27th of January 2017 12:17:49 PM
Old 01-27-2017
Quote:
Originally Posted by Peasant
If i'm not mistaken backquotes are still the lowest common denominator for command substitution if you wish your scripts to work anywhere without touching
This is an interesting argument.

IMHO the "gold standard" of portability is POSIX: if something is POSIX, then it can (and should) be used, if it not, it should be handled with extreme care (and eventually not be used in absence of compelling reasons why it should).

The construct $(..) now is in fact the POSIX-standard for doing this (subshells) and backticks `...` are deprecated. This is why i use the former rather than the latter and recommend this practice to others.

For the same reason i write i.e. tail -n 5 instead of tail -5. The former is POSIX, the latter deprecated. It may be that there is some (really old) system out there which would not recognise the new syntax but only the old one. This risk i am willing to take because, on the the other hand, there might be a really new system which has cut off old behaviorisms and only understands the current syntax.

I hope this helps.

bakunin

Moderator's Comments:
Mod Comment PS: this discussion is very interesting but we are getting off topic in relation the threads original theme. If anyone wants to continue this i suggest to split this thread and carry on in a new one. Just post here if you want to contribute and i will take care of the splitting if there are any takers.
 

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standards(5)							File Formats Manual						      standards(5)

NAME
standards - UNIX standards behavior on HP-UX DESCRIPTION
HP-UX conforms to various UNIX standards. In some cases, these standards conflict. This manpage describes the methods that programmers and users must follow to have an application conform and execute according to a particular UNIX standard. UNIX Standard Conformant Programmer Environment The following table lists feature test macros and environment variables that must be defined while compiling an application. Both a fea- ture test macro and an environment variable must be defined while compiling the application so that the application conforms and executes according to a particular UNIX standard. Otherwise, the behavior is undefined. Standard Feature Test Macros to be Environment variable defined during compilation to be set UNIX 95 _XOPEN_SOURCE_EXTENDED=1 UNIX95 or UNIX_STD=95 or UNIX_STD=1995 UNIX 2003 _XOPEN_SOURCE=600 UNIX_STD=2003 The compiler uses the feature test macros to obtain the appropriate namespace from the header files. The compiler uses the environment variable to link in an appropriate object file to the executable. Using the environment variable customizes libc to match UNIX standards for various functions. If an application has already been compiled for default HP-UX behavior or for one particular standard, and needs to change to a particular UNIX standard behavior, recompile the application as specified in the above table. For an HP-UX command to conform to a particular UNIX standard behavior, the application has to set the corresponding environment variable as specified in the above table before executing that command. UNIX Standard Conformant User Environment To enable a particular UNIX standard conformant user environment, set the corresponding environment variable as defined in the above table. EXAMPLES
The following examples shows an application example. To have the system be conformant to UNIX2003 behavior, set the environment variable to and define the feature test macro before compilation. The following example changes the command to have UNIX95 behavior by setting one of the environment variables to or to before executing that command. There are three ways of setting the environment variable for UNIX95: or or SEE ALSO
cc(1), stdsyms(5). standards(5)
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