Create a small library function, check_utility_compat(3), to determine
whether a named utility should behave in FreeBSD 4.x-compatible mode or in a standard mode (default standard). The configuration is done malloc(3)-style, with either an environment variable or a symlink. Update expr(1) to use this new interface.
This commit is contained in:
Garrett Wollman
parent
4e08ccb2ff
commit
c9885518de
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=106065
@ -121,9 +121,23 @@ otherwise 0.
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.Pp
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Parentheses are used for grouping in the usual manner.
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.Pp
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Unless the
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.Ev EXPR_COMPAT
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variable is defined in the process environment, this version of
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The
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.Nm
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utility makes no lexical distinction between arguments which may be
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operators and arguments which may be operands.
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An operand which is lexically identical to an operator will be considered a
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syntax error.
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See the examples below for a work-around.
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.Pp
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The syntax of the
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.Nm
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command in general is historic and inconvenient.
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New applications are advised to use shell arithmetic rather than
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.Nm .
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.Ss Compatibility with previous implementations
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Unless
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.Fx 4.x
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compatibility is enabled, this version of
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.Nm
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adheres to the
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\*[Px]
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@ -140,43 +154,31 @@ will not permit this syntax.
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See the examples below for portable ways to guarantee the correct
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interpretation.
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The
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.Ev EXPR_COMPAT
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variable is intended for use as a transition and debugging aid, when
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.Xr check_utility_compat 3
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function (with a
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.Fa utility
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argument of
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.Dq Li expr )
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is used to determine whether compatibility mode should be enabled.
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This feature is intended for use as a transition and debugging aid, when
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.Nm
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is used in complex scripts which cannot easily be recast to avoid the
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non-portable usage.
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Defining
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.Ev EXPR_COMPAT
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Enabling compatibility mode
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also implicitly enables the
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.Fl e
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option, since this matches the historic behavior of
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.Nm
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in
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.Fx .
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For historical reasons, defining the environment variable
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.Ev EXPR_COMPAT
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also enables compatibility mode.
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.Pp
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The
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.Nm
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utility makes no lexical distinction between arguments which may be
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operators and arguments which may be operands.
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An operand which is lexically identical to an operator will be considered a
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syntax error.
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See the examples below for a work-around.
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.Pp
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The syntax of the
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.Nm
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command in general is historic and inconvenient.
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New applications are advised to use shell arithmetic rather than
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.Nm .
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.Sh ENVIRONMENT
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.Bl -tag -width ".Ev EXPR_COMPAT"
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.It Ev EXPR_COMPAT
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If set,
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.Nm
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will emulate historic
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.Nm
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implementations which did not obey the Utility Syntax Guidelines.
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Implies
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.Fl e .
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If set, enables compatibility mode.
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.El
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.Sh EXAMPLES
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.Bl -bullet
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@ -248,15 +250,14 @@ the expression is invalid.
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.El
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.Sh SEE ALSO
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.Xr sh 1 ,
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.Xr test 1
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.Xr test 1 ,
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.Xr check_utility_compat 3
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.Sh STANDARDS
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The
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.Nm
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utility conforms to
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.St -p1003.1-2001 ,
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provided that the
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.Ev EXPR_COMPAT
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environment variable is not defined.
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provided that compatibility mode is not enabled.
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The
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.Fl e
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flag is an extension.
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@ -278,7 +278,8 @@ main(int argc, char *argv[])
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int c;
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setlocale (LC_ALL, "");
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if (getenv("EXPR_COMPAT") != NULL) {
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if (getenv("EXPR_COMPAT") != NULL
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|| check_utility_compat("expr")) {
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av = argv + 1;
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eflag = 1;
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} else {
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@ -437,6 +437,7 @@ struct timeval; /* select(2) */
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int acct(const char *);
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int async_daemon(void);
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int brk(const void *);
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int check_utility_compat(const char *);
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int chroot(const char *);
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const char *
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crypt_get_format(void);
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@ -5,7 +5,7 @@
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.PATH: ${.CURDIR}/../libc/${MACHINE_ARCH}/gen ${.CURDIR}/../libc/gen
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SRCS+= __xuname.c _pthread_stubs.c _rand48.c _spinlock_stub.c _thread_init.c \
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alarm.c arc4random.c assert.c basename.c \
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alarm.c arc4random.c assert.c basename.c check_utility_compat.c \
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clock.c closedir.c confstr.c \
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crypt.c ctermid.c daemon.c devname.c dirname.c disklabel.c \
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dlfcn.c dlfunc.c drand48.c erand48.c err.c errlst.c errno.c \
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@ -38,7 +38,7 @@ SRCS+= __xuname.c _pthread_stubs.c _rand48.c _spinlock_stub.c _thread_init.c \
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.if ${LIB} == "c"
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MAN+= alarm.3 arc4random.3 \
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basename.3 clock.3 \
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basename.3 check_utility_compat.3 clock.3 \
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confstr.3 ctermid.3 daemon.3 \
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devname.3 directory.3 dirname.3 dladdr.3 dllockinit.3 dlopen.3 \
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err.3 exec.3 fmtcheck.3 fmtmsg.3 fnmatch.3 frexp.3 ftok.3 fts.3 \
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89
lib/libc/gen/check_utility_compat.3
Normal file
89
lib/libc/gen/check_utility_compat.3
Normal file
@ -0,0 +1,89 @@
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.\"
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.\" Copyright 2002 Massachusetts Institute of Technology
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.\"
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.\" Permission to use, copy, modify, and distribute this software and
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.\" its documentation for any purpose and without fee is hereby
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.\" granted, provided that both the above copyright notice and this
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.\" permission notice appear in all copies, that both the above
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.\" copyright notice and this permission notice appear in all
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.\" supporting documentation, and that the name of M.I.T. not be used
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.\" in advertising or publicity pertaining to distribution of the
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.\" software without specific, written prior permission. M.I.T. makes
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.\" no representations about the suitability of this software for any
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.\" purpose. It is provided "as is" without express or implied
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.\" warranty.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
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.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
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.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
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.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd October 27, 2002
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.Dt CHECK_UTILITY_COMPAT 3
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.Os
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.Sh MAME
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.Nm check_utility_compat
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.Nd "determine whether a utility should be compatible"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn check_utility_compat "const char *utility"
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.Sh DESCRIPTION
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The
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.Nm
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function checks whether
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.Fa utility
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should behave in a traditional
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.Pq Fx 4.7 -compatible
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manner, or in accordance with
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.St -p1003.1-2001 .
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The configuration is given as a comma-separated list of utility names;
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if the list is present but empty, all supported utilities assume their
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most compatible mode.
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The
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.Nm
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function first checks for an environment variable named
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.Ev _COMPAT_FreeBSD_4 .
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If that environment variable does not exist, then
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.Nm
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will attempt to read the contents of a symbolic link named
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.Pa /etc/compat-FreeBSD-4-util .
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If no configuration is found, compatibility mode is disabled.
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.Sh RETURN VALUES
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The
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.Nm
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function returns zero if
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.Fa utility
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should implement strict
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.St -p1003.1-2001
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behavior, and nonzero otherwise.
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.Sh ERRORS
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No errors are detected.
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.Sh FILES
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.Bl -tag -offset indent -width Pa
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.It Pa /etc/compat-FreeBSD-4-util
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If present, a symbolic link whose expansion gives system-wide default settings
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for the
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.Nm
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function.
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.El
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.Sh HISTORY
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The
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.Nm
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function first appeared in
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.Fx 5.0 .
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.Sh AUTHOR
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This manual page was written by
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.An Garrett Wollman Aq wollman@FreeBSD.org .
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75
lib/libc/gen/check_utility_compat.c
Normal file
75
lib/libc/gen/check_utility_compat.c
Normal file
@ -0,0 +1,75 @@
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/*
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* Copyright 2002 Massachusetts Institute of Technology
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*
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* Permission to use, copy, modify, and distribute this software and
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* its documentation for any purpose and without fee is hereby
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* granted, provided that both the above copyright notice and this
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* permission notice appear in all copies, that both the above
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* copyright notice and this permission notice appear in all
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* supporting documentation, and that the name of M.I.T. not be used
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* in advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission. M.I.T. makes
|
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* no representations about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied
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* warranty.
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*
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* THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
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* ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
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* SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*
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* I din't use "namespace.h" here because none of the relevant utilities
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* are threaded, so I'm not concerned about cancellation points or other
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* niceties.
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*/
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#ifndef LINE_MAX
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#define LINE_MAX _POSIX2_LINE_MAX
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#endif
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#define _PATH_UTIL_COMPAT "/etc/compat-FreeBSD-4-util"
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#define _ENV_UTIL_COMPAT "_COMPAT_FreeBSD_4"
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int
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check_utility_compat(const char *utility)
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{
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char buf[LINE_MAX];
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char *p, *bp;
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int len;
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if ((p = getenv(_ENV_UTIL_COMPAT)) != NULL) {
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strlcpy(buf, p, sizeof buf);
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} else {
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if ((len = readlink(_PATH_UTIL_COMPAT, buf, sizeof buf)) < 0)
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return 0;
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if (len > sizeof buf)
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len = sizeof buf;
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buf[len] = '\0';
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}
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if (buf[0] == '\0')
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return 1;
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bp = buf;
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while ((p = strsep(&bp, ",")) != NULL) {
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if (strcmp(p, utility) == 0)
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return 1;
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}
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return 0;
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}
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