Add a -s flag for the same functionality as strace. Introduce a Name

type which is a String type that has no -s limitations applied to it.
Change most Strings in the code to Names and add a few extra syscalls,
namely munmap, read, rename and symlink.  This was enough to facilitate
following file descriptor allocations in the code more easily and
getting a hint at what's being read/written from/to files.  More
syscalls should really be added.

While here, fix an off-by-one bug in the buffer truncation code and
add a fflush so that truss's output reflects the syscall that the
program is stuck in.

Sponsored by:	Sophos/Activestate
MFC after:	2 weeks

13 files changed, 91 insertions, 54 deletions

diff --git a/usr.bin/truss/alpha-fbsd.c b/usr.bin/truss/alpha-fbsd.c
index 5e7fa99..7afcaa8 100644
--- a/usr.bin/truss/alpha-fbsd.c
+++ b/usr.bin/truss/alpha-fbsd.c
@@ -238,7 +238,7 @@ alpha_syscall_entry(struct trussinfo *trussinfo, int nargs) {
 	      i < (fsc.nargs - 1) ? "," : "");
 #endif
       if (sc && !(sc->args[i].type & OUT)) {
-	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0);
+	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0, trussinfo);
       }
     }
 #if DEBUG
@@ -342,7 +342,7 @@ alpha_syscall_exit(struct trussinfo *trussinfo, int syscall_num __unused)
 	if (errorp)
 	  asprintf(&temp, "0x%lx", fsc.args[sc->args[i].offset]);
 	else
-	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval);
+	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval, trussinfo);
 	fsc.s_args[i] = temp;
       }
     }
diff --git a/usr.bin/truss/amd64-fbsd.c b/usr.bin/truss/amd64-fbsd.c
index 7fb5d26..701813b 100644
--- a/usr.bin/truss/amd64-fbsd.c
+++ b/usr.bin/truss/amd64-fbsd.c
@@ -223,7 +223,7 @@ amd64_syscall_entry(struct trussinfo *trussinfo, int nargs) {
 	      i < (fsc.nargs - 1) ? "," : "");
 #endif
       if (sc && !(sc->args[i].type & OUT)) {
-	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0);
+	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0, trussinfo);
       }
     }
 #if DEBUG
@@ -327,7 +327,7 @@ amd64_syscall_exit(struct trussinfo *trussinfo, int syscall_num __unused)
 	if (errorp)
 	  asprintf(&temp, "0x%lx", fsc.args[sc->args[i].offset]);
 	else
-	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval);
+	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval, trussinfo);
 	fsc.s_args[i] = temp;
       }
     }
diff --git a/usr.bin/truss/amd64-fbsd32.c b/usr.bin/truss/amd64-fbsd32.c
index 45da1cd..d9ee202 100644
--- a/usr.bin/truss/amd64-fbsd32.c
+++ b/usr.bin/truss/amd64-fbsd32.c
@@ -217,7 +217,7 @@ i386_syscall_entry(struct trussinfo *trussinfo, int nargs) {
 	      i < (fsc.nargs - 1) ? "," : "");
 #endif
       if (sc && !(sc->args[i].type & OUT)) {
-	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0);
+	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0, trussinfo);
       }
     }
 #if DEBUG
@@ -322,7 +322,7 @@ i386_syscall_exit(struct trussinfo *trussinfo, int syscall_num __unused)
 	if (errorp)
 	  asprintf(&temp, "0x%lx", fsc.args[sc->args[i].offset]);
 	else
-	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval);
+	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval, trussinfo);
 	fsc.s_args[i] = temp;
       }
     }
diff --git a/usr.bin/truss/amd64-linux32.c b/usr.bin/truss/amd64-linux32.c
index 01703b5..9833829 100644
--- a/usr.bin/truss/amd64-linux32.c
+++ b/usr.bin/truss/amd64-linux32.c
@@ -200,7 +200,7 @@ i386_linux_syscall_entry(struct trussinfo *trussinfo, int nargs) {
 	      i < (fsc.nargs - 1) ? "," : "");
 #endif
       if (sc && !(sc->args[i].type & OUT)) {
-	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0);
+	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0, trussinfo);
       }
     }
 #if DEBUG
@@ -312,7 +312,7 @@ i386_linux_syscall_exit(struct trussinfo *trussinfo, int syscall_num __unused)
 	if (errorp)
 	  asprintf(&temp, "0x%lx", fsc.args[sc->args[i].offset]);
 	else
-	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval);
+	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval, trussinfo);
 	fsc.s_args[i] = temp;
       }
     }
diff --git a/usr.bin/truss/i386-fbsd.c b/usr.bin/truss/i386-fbsd.c
index 45da1cd..d9ee202 100644
--- a/usr.bin/truss/i386-fbsd.c
+++ b/usr.bin/truss/i386-fbsd.c
@@ -217,7 +217,7 @@ i386_syscall_entry(struct trussinfo *trussinfo, int nargs) {
 	      i < (fsc.nargs - 1) ? "," : "");
 #endif
       if (sc && !(sc->args[i].type & OUT)) {
-	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0);
+	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0, trussinfo);
       }
     }
 #if DEBUG
@@ -322,7 +322,7 @@ i386_syscall_exit(struct trussinfo *trussinfo, int syscall_num __unused)
 	if (errorp)
 	  asprintf(&temp, "0x%lx", fsc.args[sc->args[i].offset]);
 	else
-	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval);
+	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval, trussinfo);
 	fsc.s_args[i] = temp;
       }
     }
diff --git a/usr.bin/truss/i386-linux.c b/usr.bin/truss/i386-linux.c
index 01703b5..9833829 100644
--- a/usr.bin/truss/i386-linux.c
+++ b/usr.bin/truss/i386-linux.c
@@ -200,7 +200,7 @@ i386_linux_syscall_entry(struct trussinfo *trussinfo, int nargs) {
 	      i < (fsc.nargs - 1) ? "," : "");
 #endif
       if (sc && !(sc->args[i].type & OUT)) {
-	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0);
+	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0, trussinfo);
       }
     }
 #if DEBUG
@@ -312,7 +312,7 @@ i386_linux_syscall_exit(struct trussinfo *trussinfo, int syscall_num __unused)
 	if (errorp)
 	  asprintf(&temp, "0x%lx", fsc.args[sc->args[i].offset]);
 	else
-	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval);
+	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval, trussinfo);
 	fsc.s_args[i] = temp;
       }
     }
diff --git a/usr.bin/truss/ia64-fbsd.c b/usr.bin/truss/ia64-fbsd.c
index 7ca6d7f..10fcd62 100644
--- a/usr.bin/truss/ia64-fbsd.c
+++ b/usr.bin/truss/ia64-fbsd.c
@@ -204,7 +204,7 @@ ia64_syscall_entry(struct trussinfo *trussinfo, int nargs) {
 	      i < (fsc.nargs - 1) ? "," : "");
 #endif
       if (sc && !(sc->args[i].type & OUT)) {
-	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0);
+	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0, trussinfo);
       }
     }
 #if DEBUG
@@ -308,7 +308,7 @@ ia64_syscall_exit(struct trussinfo *trussinfo, int syscall_num __unused)
 	if (errorp)
 	  asprintf(&temp, "0x%lx", fsc.args[sc->args[i].offset]);
 	else
-	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval);
+	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval, trussinfo);
 	fsc.s_args[i] = temp;
       }
     }
diff --git a/usr.bin/truss/main.c b/usr.bin/truss/main.c
index 9d289a7..6866e71 100644
--- a/usr.bin/truss/main.c
+++ b/usr.bin/truss/main.c
@@ -70,8 +70,8 @@ static void
 usage(void)
 {
 	fprintf(stderr, "%s\n%s\n",
-	    "usage: truss [-faedDS] [-o file] -p pid",
-	    "       truss [-faedDS] [-o file] command [args]");
+	    "usage: truss [-faedDS] [-o file] [-s strsize] -p pid",
+	    "       truss [-faedDS] [-o file] [-s strsize] command [args]");
 	exit(1);
 }
 
@@ -181,8 +181,9 @@ main(int ac, char **av)
 		errx(1, "malloc() failed");
 	bzero(trussinfo, sizeof(struct trussinfo));
 	trussinfo->outfile = stderr;
+	trussinfo->strsize = 32;
 
-	while ((c = getopt(ac, av, "p:o:faedDS")) != -1) {
+	while ((c = getopt(ac, av, "p:o:faedDs:S")) != -1) {
 		switch (c) {
 		case 'p':	/* specified pid */
 			trussinfo->pid = atoi(optarg);
@@ -205,6 +206,9 @@ main(int ac, char **av)
 		case 'o':	/* Specified output file */
 			fname = optarg;
 			break;
+		case 's':	/* Specified string size */
+			trussinfo->strsize = atoi(optarg);
+			break;
 		case 'S':	/* Don't trace signals */ 
 			trussinfo->flags |= NOSIGS;
 			break;
diff --git a/usr.bin/truss/sparc64-fbsd.c b/usr.bin/truss/sparc64-fbsd.c
index 375e1fa..d30dc23 100644
--- a/usr.bin/truss/sparc64-fbsd.c
+++ b/usr.bin/truss/sparc64-fbsd.c
@@ -240,7 +240,7 @@ sparc64_syscall_entry(struct trussinfo *trussinfo, int nargs) {
 	      i < (fsc.nargs - 1) ? "," : "");
 #endif
       if (sc && !(sc->args[i].type & OUT)) {
-	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0);
+	fsc.s_args[i] = print_arg(Procfd, &sc->args[i], fsc.args, 0, trussinfo);
       }
     }
 #if DEBUG
@@ -343,7 +343,7 @@ sparc64_syscall_exit(struct trussinfo *trussinfo, int syscall_num __unused) {
 	if (errorp)
 	  asprintf(&temp, "0x%lx", fsc.args[sc->args[i].offset]);
 	else
-	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval);
+	  temp = print_arg(Procfd, &sc->args[i], fsc.args, retval, trussinfo);
 	fsc.s_args[i] = temp;
       }
     }
diff --git a/usr.bin/truss/syscall.h b/usr.bin/truss/syscall.h
index 838dfe2..2783486 100644
--- a/usr.bin/truss/syscall.h
+++ b/usr.bin/truss/syscall.h
@@ -30,7 +30,7 @@
  * $FreeBSD$
  */
 
-enum Argtype { None = 1, Hex, Octal, Int, String, Ptr, Stat, Ioctl, Quad,
+enum Argtype { None = 1, Hex, Octal, Int, Name, String, Ptr, Stat, Ioctl, Quad,
 	Signal, Sockaddr, StringArray, Timespec, Timeval, Itimerval, Pollfd, 
 	Fd_set, Sigaction, Fcntl, Mprot, Mmapflags, Whence, Readlinkres };
 
@@ -53,7 +53,7 @@ struct syscall {
 
 struct syscall *get_syscall(const char*);
 char *get_string(int, void*, int);
-char *print_arg(int, struct syscall_args *, unsigned long*, long);
+char *print_arg(int, struct syscall_args *, unsigned long*, long, struct trussinfo *);
 void print_syscall(struct trussinfo *, const char *, int, char **);
 void print_syscall_ret(struct trussinfo *, const char *, int, char **, int,
     long);
diff --git a/usr.bin/truss/syscalls.c b/usr.bin/truss/syscalls.c
index 52d7885..b94df2d 100644
--- a/usr.bin/truss/syscalls.c
+++ b/usr.bin/truss/syscalls.c
@@ -71,7 +71,7 @@ struct syscall syscalls[] = {
 	{ "fcntl", 1, 3,
 	  { { Int, 0 } , { Fcntl, 1 }, { Hex, 2 }}},
 	{ "readlink", 1, 3,
-	  { { String, 0 } , { Readlinkres | OUT, 1 }, { Int, 2 }}},
+	  { { Name, 0 } , { Readlinkres | OUT, 1 }, { Int, 2 }}},
 	{ "lseek", 2, 3,
 #ifdef __LP64__
 	  { { Int, 0 }, {Quad, 2 }, { Whence, 3 }}},
@@ -89,48 +89,48 @@ struct syscall syscalls[] = {
 	{ "mprotect", 1, 3,
 	  { { Ptr, 0 }, {Int, 1}, {Mprot, 2}}},
 	{ "open", 1, 3,
-	  { { String | IN, 0} , { Hex, 1}, {Octal, 2}}},
+	  { { Name | IN, 0} , { Hex, 1}, {Octal, 2}}},
 	{ "mkdir", 1, 2,
-	  { { String, 0} , {Octal, 1}}},
+	  { { Name, 0} , {Octal, 1}}},
 	{ "linux_open", 1, 3,
-	  { { String, 0 }, { Hex, 1}, { Octal, 2 }}},
+	  { { Name, 0 }, { Hex, 1}, { Octal, 2 }}},
 	{ "close", 1, 1,
 	  { { Int, 0 } } },
 	{ "link", 0, 2,
-	  { { String, 0 }, { String, 1 }}},
+	  { { Name, 0 }, { Name, 1 }}},
 	{ "unlink", 0, 1,
-	  { { String, 0 }}},
+	  { { Name, 0 }}},
 	{ "chdir", 0, 1,
-	  { { String, 0 }}},
+	  { { Name, 0 }}},
 	{ "chroot", 0, 1,
-	  { { String, 0 }}},
+	  { { Name, 0 }}},
 	{ "mknod", 0, 3,
-	  { { String, 0 }, { Octal, 1 }, { Int, 3 }}},
+	  { { Name, 0 }, { Octal, 1 }, { Int, 3 }}},
 	{ "chmod", 0, 2,
-	  { { String, 0 }, { Octal, 1 }}},
+	  { { Name, 0 }, { Octal, 1 }}},
 	{ "chown", 0, 3,
-	  { { String, 0 }, { Int, 1 }, { Int, 2 }}},
+	  { { Name, 0 }, { Int, 1 }, { Int, 2 }}},
 	{ "mount", 0, 4,
-	  { { String, 0 }, { String, 1 }, { Int, 2 }, { Ptr, 3 }}},
+	  { { Name, 0 }, { Name, 1 }, { Int, 2 }, { Ptr, 3 }}},
 	{ "umount", 0, 2,
-	  { { String, 0 }, { Int, 2 }}},
+	  { { Name, 0 }, { Int, 2 }}},
 	{ "fstat", 1, 2,
 	  { { Int, 0},  {Ptr | OUT , 1 }}},
 	{ "stat", 1, 2,
-	  { { String | IN, 0 }, { Ptr | OUT, 1 }}},
+	  { { Name | IN, 0 }, { Ptr | OUT, 1 }}},
 	{ "lstat", 1, 2,
-	  { { String | IN, 0 }, { Ptr | OUT, 1 }}},
+	  { { Name | IN, 0 }, { Ptr | OUT, 1 }}},
 	{ "linux_newstat", 1, 2,
-	  { { String | IN, 0 }, { Ptr | OUT, 1 }}},
+	  { { Name | IN, 0 }, { Ptr | OUT, 1 }}},
 	{ "linux_newfstat", 1, 2,
 	  { { Int, 0 }, { Ptr | OUT, 1 }}},
 	{ "write", 1, 3,
-	  { { Int, 0 }, { Ptr | IN, 1 }, { Int, 2 }}},
+	  { { Int, 0 }, { String | IN, 1 }, { Int, 2 }}},
 	{ "ioctl", 1, 3,
 	  { { Int, 0 }, { Ioctl, 1 }, { Hex, 2 }}},
 	{ "break", 1, 1, { { Hex, 0 }}},
 	{ "exit", 0, 1, { { Hex, 0 }}},
-	{ "access", 1, 2, { { String | IN, 0 }, { Int, 1 }}},
+	{ "access", 1, 2, { { Name | IN, 0 }, { Int, 1 }}},
 	{ "sigaction", 1, 3,
 	  { { Signal, 0 }, { Sigaction | IN, 1 }, { Sigaction | OUT, 2 }}},
 	{ "accept", 1, 3,
@@ -148,12 +148,12 @@ struct syscall syscalls[] = {
 	{ "sendto", 1, 6,
 	  { { Hex, 0 }, { Ptr | IN, 1 }, { Int, 3 }, { Hex, 3 }, { Sockaddr | IN, 4 }, { Ptr | IN, 5 } } },
 	{ "execve", 1, 3,
-	  { { String | IN, 0 }, { StringArray | IN, 1 }, { StringArray | IN, 2 } } },
+	  { { Name | IN, 0 }, { StringArray | IN, 1 }, { StringArray | IN, 2 } } },
 	{ "linux_execve", 1, 3,
-	  { { String | IN, 0 }, { StringArray | IN, 1 }, { StringArray | IN, 2 } } },
-	{ "kldload", 0, 1, { { String | IN, 0 }}},
+	  { { Name | IN, 0 }, { StringArray | IN, 1 }, { StringArray | IN, 2 } } },
+	{ "kldload", 0, 1, { { Name | IN, 0 }}},
 	{ "kldunload", 0, 1, { { Int, 0 }}},
-	{ "kldfind", 0, 1, { { String | IN, 0 }}},
+	{ "kldfind", 0, 1, { { Name | IN, 0 }}},
 	{ "kldnext", 0, 1, { { Int, 0 }}},
 	{ "kldstat", 0, 2, { { Int, 0 }, { Ptr, 1 }}},
 	{ "kldfirstmod", 0, 1, { { Int, 0 }}},
@@ -166,15 +166,23 @@ struct syscall syscalls[] = {
 	{ "getitimer", 1, 2, { { Int, 0 }, { Itimerval | OUT, 2 }}},
 	{ "setitimer", 1, 3, { { Int, 0 }, { Itimerval, 1} , { Itimerval | OUT, 2 }}},
 	{ "utimes", 1, 2,
-		{ { String | IN, 0 }, { Timeval | IN, 1 }}},
+		{ { Name | IN, 0 }, { Timeval | IN, 1 }}},
 	{ "lutimes", 1, 2,
-		{ { String | IN, 0 }, { Timeval | IN, 1 }}},
+		{ { Name | IN, 0 }, { Timeval | IN, 1 }}},
 	{ "futimes", 1, 2,
 		{ { Int, 0 }, { Timeval | IN, 1 }}},
 	{ "chflags", 1, 2,
-		{ { String | IN, 0 }, { Hex, 1 }}},
+		{ { Name | IN, 0 }, { Hex, 1 }}},
 	{ "lchflags", 1, 2,
-		{ { String | IN, 0 }, { Hex, 1 }}},
+		{ { Name | IN, 0 }, { Hex, 1 }}},
+	{ "munmap", 1, 2,
+		{ { Ptr, 0 }, { Int, 1 }}},
+	{ "read", 1, 3,
+	  { { Int, 0}, { String | OUT, 1}, { Int, 2}}},
+	{ "rename", 1, 2,
+	  { { Name , 0} , { Name, 1}}},
+	{ "symlink", 1, 2,
+	  { { Name , 0} , { Name, 1}}},
 	{ 0, 0, 0, { { 0, 0 }}},
 };
 
@@ -228,16 +236,14 @@ get_string(int procfd, void *offset, int max) {
 		err(1, "dup");
 	if ((p = fdopen(fd, "r")) == NULL)
 		err(1, "fdopen");
-	buf = malloc( size = (max ? max : 64 ) );
+	buf = malloc( size = (max ? max + 1 : 64 ) );
 	len = 0;
 	buf[0] = 0;
 	if (fseeko(p, (uintptr_t)offset, SEEK_SET) == 0) {
 		while ((c = fgetc(p)) != EOF) {
 			buf[len++] = c;
-			if (c == 0 || len == max) {
-				buf[len] = 0;
+			if (c == 0 || len == max)
 				break;
-			}
 			if (len == size) {
 				char *tmp;
 				tmp = realloc(buf, size+64);
@@ -249,6 +255,7 @@ get_string(int procfd, void *offset, int max) {
 				buf = tmp;
 			}
 		}
+		buf[len] = 0;
 	}
 	fclose(p);
 	return (buf);
@@ -279,8 +286,10 @@ remove_trailing_or(char *str)
  */
 
 char *
-print_arg(int fd, struct syscall_args *sc, unsigned long *args, long retval) {
+print_arg(int fd, struct syscall_args *sc, unsigned long *args, long retval, struct trussinfo *trussinfo) {
   char *tmp = NULL;
+  int max = 0;
+
   switch (sc->type & ARG_MASK) {
   case Hex:
     asprintf(&tmp, "0x%lx", args[sc->offset]);
@@ -292,10 +301,20 @@ print_arg(int fd, struct syscall_args *sc, unsigned long *args, long retval) {
     asprintf(&tmp, "%ld", args[sc->offset]);
     break;
   case String:
+    max = trussinfo->strsize;
+    if (max == 0)
+    {
+      asprintf(&tmp, "0x%lx", args[sc->offset]);
+      break;
+    }
+  case Name:
     {
       char *tmp2;
-      tmp2 = get_string(fd, (void*)args[sc->offset], 0);
-      asprintf(&tmp, "\"%s\"", tmp2);
+      tmp2 = get_string(fd, (void*)args[sc->offset], max ? max + 1 : 0);
+      if (max && memchr(tmp2, '\0', max + 1) == NULL)
+        asprintf(&tmp, "\"%.*s...\"", max, tmp2);
+      else
+        asprintf(&tmp, "\"%s\"", tmp2);
       free(tmp2);
     }
   break;
@@ -729,6 +748,7 @@ print_syscall_ret(struct trussinfo *trussinfo, const char *name, int nargs,
     char **s_args, int errorp, long retval)
 {
   print_syscall(trussinfo, name, nargs, s_args);
+  fflush(trussinfo->outfile);
   if (errorp) {
     fprintf(trussinfo->outfile, " ERR#%ld '%s'\n", retval, strerror(retval));
   } else {
diff --git a/usr.bin/truss/truss.1 b/usr.bin/truss/truss.1
index 6b975ba..3efa65f 100644
--- a/usr.bin/truss/truss.1
+++ b/usr.bin/truss/truss.1
@@ -10,10 +10,12 @@
 .Nm
 .Op Fl faedDS
 .Op Fl o Ar file
+.Op Fl s Ar strsize
 .Fl p Ar pid
 .Nm
 .Op Fl faedDS
 .Op Fl o Ar file
+.Op Fl s Ar strsize
 command
 .Op args
 .Sh DESCRIPTION
@@ -54,6 +56,16 @@ displays signal as well as system call events.)
 Print the output to the specified
 .Ar file
 instead of standard error.
+.It Fl s Ar strsize
+Display strings using at most
+.Ar strsize
+characters.
+If the buffer is larger,
+.Qq ...
+will be displayed at the end of the string.
+The default
+.Ar strsize
+is 32.
 .It Fl p Ar pid
 Follow the process specified by
 .Ar pid
diff --git a/usr.bin/truss/truss.h b/usr.bin/truss/truss.h
index 00df4d6..24558ba 100644
--- a/usr.bin/truss/truss.h
+++ b/usr.bin/truss/truss.h
@@ -37,6 +37,7 @@ struct trussinfo
 	int pid;
 	int flags;
 	int in_fork;
+	int strsize;
 	FILE *outfile;
 
 	struct timespec start_time;