We invoke shell commands in a Makefile, and if we are concerned about POSIX conformance in the Makefile syntax, we need to be equally concerned about POSIX conf

We invoke shell commands in a Makefile, and if we are concerned about POSIX conformance in the Makefile syntax, we need to be equally concerned about POSIX conformance in the shell commands and the shell scripts we invoke in Makefile. While I have not found a foolproof way to test for and prove POSIX conformance in shell scripts, I usually go through the POSIX.1-2001 documents to make sure I am limiting my code to features specified in POSIX. I test the scripts with bash, ksh, and zsh on Debian and Mac. Then I also test the scripts with dash, posh and yash on Debian. See https://github.com/susam/vimer/blob/master/Makefile https://github.com/susam/vimer/blob/master/Makefile for an example. Here are some resources: * POSIX.1-2001 (2004 edition home): http://pubs.opengroup.org/onlinepubs/009695399/ http://pubs.opengroup.org/onlinepubs/009695399/ * POSIX.1-2001 (Special Built-In Utilities): http://pubs.opengroup.org/onlinepubs/009695399/idx/sbi.html http://pubs.opengroup.org/onlinepubs/009695399/idx/sbi.html * POSIX.1-2001 (Utilities): http://pubs.opengroup.org/onlinepubs/009695399/idx/utilities.html http://pubs.opengroup.org/onlinepubs/009695399/idx/utilities... * POSIX.1-2008 (2016 edition home): http://pubs.opengroup.org/onlinepubs/9699919799/ http://pubs.opengroup.org/onlinepubs/9699919799/ * POSIX.1-2008 (Special Built-In Utilities): http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_14 http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3... * POSIX.1-2008 (Utilities): http://pubs.opengroup.org/onlinepubs/9699919799/idx/utilities.html http://pubs.opengroup.org/onlinepubs/9699919799/idx/utilitie... The editions mentioned in parentheses are the editions available at the mentioned URLs at the time of posting this comment. Here is a list of the commands specified in POSIX: Special Built-In Utilities: break, colon, continue, dot, eval, exec, exit, export, readonly, return, set, shift, times, trap, unset Utilities: admin, alias, ar, asa, at, awk, basename, batch, bc, bg, c99, cal, cat, cd, cflow, chgrp, chmod, chown, cksum, cmp, comm, command, compress, cp, crontab, csplit, ctags, cut, cxref, date, dd, delta, df, diff, dirname, du, echo, ed, env, ex, expand, expr, false, fc, fg, file, find, fold, fort77, fuser, gencat, get, getconf, getopts, grep, hash, head, iconv, id, ipcrm, ipcs, jobs, join, kill, lex, link, ln, locale, localedef, logger, logname, lp, ls, m4, mailx, make, man, mesg, mkdir, mkfifo, more, mv, newgrp, nice, nl, nm, nohup, od, paste, patch, pathchk, pax, pr, printf, prs, ps, pwd, qalter, qdel, qhold, qmove, qmsg, qrerun, qrls, qselect, qsig, qstat, qsub, read, renice, rm, rmdel, rmdir, sact, sccs, sed, sh, sleep, sort, split, strings, strip, stty, tabs, tail, talk, tee, test, time, touch, tput, tr, true, tsort, tty, type, ulimit, umask, unalias, uname, uncompress, unexpand, unget, uniq, unlink, uucp, uudecode, uuencode, uustat, uux, val, vi, wait, wc, what, who, write, xargs, yacc, zcat