FAQ & Implementation Issues

Frequently Asked Questions

Implementation Issues

modification time and date formatting

The posix `date` command is not required to support the option "-r" to get the formatted date of a file time. The linux `stat` command would be even better but it is inherently not portable. And the `ls -l` output does (a) have a different column offset for the modification time for each `ls` implementation and (b) uses a format that can not be easily reformatted. On some unix-compatible workstations you might get interesting results. It is highly recommended to install gnu `date` to get acces to some `strftime()` command but nethertheless the mksite.sh script has been trying hard to get around the problems.

`sed` commands per anchor

The posix `sed` spec says `Historically, the sed ! and } editing commands did not permit multiple commands on a single line using a semicolon as a command delimiter. Implementations are permitted, but not required, to support this extension.`. Therefore one can not write -e  "/anchor/{h;s/x/y/g;x}" but instead it has to be -e "/anchor/{" -e "h" -e "s/x/y/g" -e  "x" -e "}". Looking closer one can see it is indeed possible to split a line by saying -e "s/xx/y\\" -e "z/" which is an escaped newline. A hint says that some implementations do not support this.

`sed` commands per file

There has been no reference in posix `sed` spec but the hpux sed command is limited to 100 lines per sed script file (it is even documented in the hpux sed manpage). This is much below the number of lines we usually generate into the ~head~ and ~body~ sed script. If you see some error like `too many arguments for command xy` then it is most probably the error `too many commands per sed script`.

Cross References

unix2003 date

http://www.opengroup.org/onlinepubs/007904975/utilities/date.html

unix2003 sed

http://www.opengroup.org/onlinepubs/007904975/utilities/sed.html

hpux(9) sed manpage

http://www.informatik.uni-frankfurt.de/doc/man/hpux/sed.1.html

sunos(5.9) sed manpage

http://bama.ua.edu/cgi-bin/man-cgi?sed+1

sunos(5.9) date manpage

http://bama.ua.edu/cgi-bin/man-cgi?date+1