pax, tar, and cpio are one binary that changes behavior based on the last component of argv[0]. Lots of shared code, so sure, but I find the strcmp() tests in the main code overly complex and perhaps an affront to clear style. (It's _not_ really a perf issue, as in per-file processing it only checks this for directories and not each file or block.)
So how about we have a enum for the mode that gets set when it decides how to parse the options and is then checked directly after that? Is this clearer? Philip Guenther Index: extern.h =================================================================== RCS file: /cvs/src/bin/pax/extern.h,v retrieving revision 1.55 diff -u -p -r1.55 extern.h --- extern.h 14 Aug 2016 04:47:52 -0000 1.55 +++ extern.h 23 Aug 2016 03:49:10 -0000 @@ -240,6 +240,7 @@ extern int exit_val; extern int docrc; extern char *dirptr; extern char *argv0; +extern enum op_mode { OP_PAX, OP_TAR, OP_CPIO } op_mode; extern FILE *listf; extern int listfd; extern char *tempfile; Index: pax.c =================================================================== RCS file: /cvs/src/bin/pax/pax.c,v retrieving revision 1.45 diff -u -p -r1.45 pax.c --- pax.c 23 Jun 2016 06:37:36 -0000 1.45 +++ pax.c 23 Aug 2016 03:49:10 -0000 @@ -90,6 +90,7 @@ int exit_val; /* exit value */ int docrc; /* check/create file crc */ char *dirptr; /* destination dir in a copy */ char *argv0; /* root of argv[0] */ +enum op_mode op_mode; /* what program are we acting as? */ sigset_t s_mask; /* signal mask for cleanup critical sect */ FILE *listf = stderr; /* file pointer to print file list to */ int listfd = STDERR_FILENO; /* fd matching listf, for sighandler output */ Index: options.c =================================================================== RCS file: /cvs/src/bin/pax/options.c,v retrieving revision 1.94 diff -u -p -r1.94 options.c --- options.c 14 Aug 2016 04:47:52 -0000 1.94 +++ options.c 23 Aug 2016 03:49:10 -0000 @@ -186,11 +186,13 @@ options(int argc, char **argv) argv0 = __progname; if (strcmp(NM_TAR, argv0) == 0) { + op_mode = OP_TAR; tar_options(argc, argv); return; } #ifndef NOCPIO else if (strcmp(NM_CPIO, argv0) == 0) { + op_mode = OP_CPIO; cpio_options(argc, argv); return; } @@ -199,6 +201,7 @@ options(int argc, char **argv) * assume pax as the default */ argv0 = NM_PAX; + op_mode = OP_PAX; pax_options(argc, argv); } Index: ar_io.c =================================================================== RCS file: /cvs/src/bin/pax/ar_io.c,v retrieving revision 1.57 diff -u -p -r1.57 ar_io.c --- ar_io.c 14 Aug 2016 18:30:33 -0000 1.57 +++ ar_io.c 23 Aug 2016 03:49:10 -0000 @@ -390,12 +390,12 @@ ar_close(int in_sig) return; } - if (strcmp(NM_PAX, argv0) == 0) + if (op_mode == OP_PAX) (void)dprintf(listfd, "%s: %s vol %d, %lu files," " %llu bytes read, %llu bytes written.\n", argv0, frmt->name, arvol-1, flcnt, rdcnt, wrcnt); #ifndef NOCPIO - else if (strcmp(NM_CPIO, argv0) == 0) + else if (op_mode == OP_CPIO) (void)dprintf(listfd, "%llu blocks\n", (rdcnt ? rdcnt : wrcnt) / 5120); #endif /* !NOCPIO */ @@ -1112,7 +1112,7 @@ ar_next(void) if (sigprocmask(SIG_SETMASK, &o_mask, NULL) < 0) syswarn(0, errno, "Unable to restore signal mask"); - if (done || !wr_trail || force_one_volume || strcmp(NM_TAR, argv0) == 0) + if (done || !wr_trail || force_one_volume || op_mode == OP_TAR) return(-1); tty_prnt("\nATTENTION! %s archive volume change required.\n", argv0); Index: file_subs.c =================================================================== RCS file: /cvs/src/bin/pax/file_subs.c,v retrieving revision 1.50 diff -u -p -r1.50 file_subs.c --- file_subs.c 23 Aug 2016 03:31:44 -0000 1.50 +++ file_subs.c 23 Aug 2016 03:49:10 -0000 @@ -371,7 +371,7 @@ node_creat(ARCHD *arcn) * potential symlink chain before trying to create the * directory. */ - if (strcmp(NM_TAR, argv0) == 0 && Lflag) { + if (op_mode == OP_TAR && Lflag) { while (lstat(nm, &sb) == 0 && S_ISLNK(sb.st_mode)) { len = readlink(nm, target, @@ -484,7 +484,7 @@ badlink: if (pmode && !defer_pmode) set_pmode(nm, arcn->sb.st_mode); - if (arcn->type == PAX_DIR && strcmp(NM_CPIO, argv0) != 0) { + if (arcn->type == PAX_DIR && op_mode != OP_CPIO) { /* * Dirs must be processed again at end of extract to set times * and modes to agree with those stored in the archive. However @@ -758,7 +758,7 @@ set_ids(char *fnm, uid_t uid, gid_t gid) * ignore EPERM unless in verbose mode or being run by root. * if running as pax, POSIX requires a warning. */ - if (strcmp(NM_PAX, argv0) == 0 || errno != EPERM || vflag || + if (op_mode == OP_PAX || errno != EPERM || vflag || geteuid() == 0) syswarn(1, errno, "Unable to set file uid/gid of %s", fnm); @@ -775,7 +775,7 @@ fset_ids(char *fnm, int fd, uid_t uid, g * ignore EPERM unless in verbose mode or being run by root. * if running as pax, POSIX requires a warning. */ - if (strcmp(NM_PAX, argv0) == 0 || errno != EPERM || vflag || + if (op_mode == OP_PAX || errno != EPERM || vflag || geteuid() == 0) syswarn(1, errno, "Unable to set file uid/gid of %s", fnm);