Make C plugin output format configurablehw/output/functions

The development guidelines¹ currently state that the plugin output
should be in the format "SERVICE STATUS: Information text".  However,
the SERVICE and STATUS information is redundant, as the plugin caller
(e.g., Nagios) should know which SERVICE is checked and the STATUS is
returned via the plugin's exit code.  After discussing² this issue on
the development list, we decided to make the plugin output configurable
at compile time (separately for "normal" and "verbose" output).

¹ http://nagiosplug.sf.net/developer-guidelines.html
² http://thread.gmane.org/gmane.network.nagios.plugins.devel/5155

Signed-off-by: Holger Weiss <hweiss@users.sourceforge.net>

5 files changed, 263 insertions, 19 deletions

diff --git a/configure.in b/configure.in
index 68ac0a0..a4b5e96 100644
--- a/configure.in
+++ b/configure.in
@@ -39,6 +39,39 @@ INSTALL="$INSTALL $extra_install_args"
 INSTALL_STRIP_PROGRAM="$INSTALL_STRIP_PROGRAM $extra_install_args"
 AC_SUBST(INSTALL)
 
+dnl Configure the plugin output format
+default_output_format="%s %x: %i\n"
+AC_ARG_WITH([standard_output_format],
+        [AS_HELP_STRING([--with-standard-output-format=FORMAT],
+                [specify the standard plugin output FORMAT; %p, %s, %x, and %m
+                 will be replaced by the plugin name, the service name, the
+                 status string, and the information message, respectively; tabs
+                 or newlines can be inserted using \t or \n
+                 @<:@default="%s %x: %m\n"@:>@])],
+        [standard_output_format=$withval],
+        [standard_output_format="yes"])
+AC_ARG_WITH([verbose_output_format],
+        [AS_HELP_STRING([--with-verbose-output-format=FORMAT],
+                [specify the verbose plugin output FORMAT; %p, %s, %x, and %m
+                 will be replaced by the plugin name, the service name, the
+                 status string, and the information message, respectively; tabs
+                 or newlines can be inserted using \t or \n
+                 @<:@default="%s %x: %m\n"@:>@])],
+        [verbose_output_format=$withval],
+        [verbose_output_format="yes"])
+AS_IF([test "$standard_output_format" = yes],
+                [standard_output_format=$default_output_format],
+        [test "$standard_output_format" = no],
+                [standard_output_format=""],
+        [test "$verbose_output_format" = yes],
+                [verbose_output_format=$default_output_format],
+        [test "$verbose_output_format" = no],
+                [verbose_output_format=""])
+AC_DEFINE_UNQUOTED([STANDARD_OUTPUT_FORMAT], ["$standard_output_format"],
+        [Define the standard plugin output format.])
+AC_DEFINE_UNQUOTED([VERBOSE_OUTPUT_FORMAT], ["$verbose_output_format"],
+        [Define the verbose plugin output format.])
+
 AC_PROG_CC
 gl_EARLY
 AC_PROG_GCC_TRADITIONAL
@@ -150,6 +183,11 @@ AC_CHECK_LIB(socket,socket,SOCKETLIBS="$SOCKETLIBS -lsocket")
 AC_CHECK_LIB(resolv,main,SOCKETLIBS="$SOCKETLIBS -lresolv")
 AC_SUBST(SOCKETLIBS)
 
+dnl check for basename(3) which needs -lgen on some systems (e.g. IRIX)
+AC_CHECK_HEADERS([libgen.h])
+AC_SEARCH_LIBS([basename], [gen])
+AC_CHECK_FUNCS([basename])
+
 dnl
 dnl check for math-related functions needing -lm
 AC_CHECK_HEADERS(math.h)
diff --git a/lib/utils_base.c b/lib/utils_base.c
index 77700f5..ba4f83b 100644
--- a/lib/utils_base.c
+++ b/lib/utils_base.c
@@ -24,10 +24,151 @@
 *
 *****************************************************************************/
 
+#if HAVE_LIBGEN_H
+#include <libgen.h>     /* basename(3) */
+#endif
+#include <stdarg.h>
 #include "common.h"
 #include <stdarg.h>
 #include "utils_base.h"
 
+#define PRINT_OUTPUT(fmt, ap)                                          \
+        do {                                                           \
+                fmt = insert_syserr(fmt);                              \
+                va_start(ap, fmt);                                     \
+                vprintf(fmt, ap);                                      \
+                va_end(ap);                                            \
+        } while (/* CONSTCOND */ 0)
+
+static char *insert_syserr(const char *);
+
+extern int errno;
+static int verbosity_level = -2;
+static const char *program_name = NULL;
+static const char *service_name = NULL;
+
+/*
+ * Set static variables for use in output functions.  Usually, argv[0] may be
+ * used as progname, since we call basename(3) ourselves.  If a verbosity value
+ * of -2 is specified, the verbosity_level won't be set.  Currently, no flags
+ * are implemented.
+ */
+void
+np_set_output(const char *progname, const char *servname, int verbosity,
+              int flags __attribute__((unused)))
+{
+        static char pathbuf[128], progbuf[128], servbuf[32];
+
+        if (progname != NULL) {
+#if HAVE_BASENAME
+                /*
+                 * Copy the progname into a temporary buffer in order to cope
+                 * with basename(3) implementations which modify their argument.
+                 * TODO: Maybe we should implement an np_basename()?  Gnulib's
+                 * base_name() dies on error, writing a message to stderr, which
+                 * is probably not what we want.  Once we have some replacement,
+                 * the libgen-/basename(3)-related checks can be removed from
+                 * configure.in.
+                 */
+                strncpy(pathbuf, progname, sizeof(pathbuf) - 1);
+                pathbuf[sizeof(pathbuf) - 1] = '\0';
+                progname = basename(pathbuf);
+#endif
+                strncpy(progbuf, progname, sizeof(progbuf) - 1);
+                progbuf[sizeof(progbuf) - 1] = '\0';
+                program_name = progbuf;
+        }
+        if (servname != NULL) {
+                strncpy(servbuf, servname, sizeof(servbuf) - 1);
+                servbuf[sizeof(servbuf) - 1] = '\0';
+                service_name = servbuf;
+        }
+        if (verbosity != -2)
+                verbosity_level = verbosity;
+}
+
+int
+np_adjust_verbosity(int by)
+{
+        if (verbosity_level == -2)
+                verbosity_level = by;
+        else
+                verbosity_level += by;
+
+        /* We don't support verbosity levels < -1. */
+        if (verbosity_level < -1)
+                verbosity_level = -1;
+
+        return verbosity_level;
+}
+
+void
+np_debug(int verbosity, const char *fmt, ...)
+{
+        va_list ap;
+
+        if (verbosity_level != -1 && verbosity >= verbosity_level)
+                PRINT_OUTPUT(fmt, ap);
+}
+
+void
+np_verbose(const char *fmt, ...)
+{
+        va_list ap;
+
+        if (verbosity_level >= 1) {
+                PRINT_OUTPUT(fmt, ap);
+                putchar('\n');
+        }
+}
+
+void
+np_die(int status, const char *fmt, ...)
+{
+        va_list ap;
+        const char *p;
+
+        if (program_name == NULL || service_name == NULL)
+                PRINT_OUTPUT(fmt, ap);
+
+        for (p = (verbosity_level > 0) ?
+            VERBOSE_OUTPUT_FORMAT : STANDARD_OUTPUT_FORMAT;
+            *p != '\0'; p++) {
+                if (*p == '%') {
+                        if (*++p == '\0')
+                                break;
+                        switch (*p) {
+                        case 'm':
+                                PRINT_OUTPUT(fmt, ap);
+                                continue;
+                        case 'p':
+                                fputs(program_name, stdout);
+                                continue;
+                        case 's':
+                                fputs(service_name, stdout);
+                                continue;
+                        case 'x':
+                                fputs(state_text(status), stdout);
+                                continue;
+                        }
+                } else if (*p == '\\') {
+                        if (*++p == '\0')
+                                break;
+                        switch (*p) {
+                        case 'n':
+                                putchar('\n');
+                                continue;
+                        case 't':
+                                putchar('\t');
+                                continue;
+                        }
+                }
+                putchar(*p);
+        }
+        exit(status);
+}
+
+/* TODO: die() can be removed as soon as all plugins use np_die() instead. */
 void
 die (int result, const char *fmt, ...)
 {
@@ -308,3 +449,67 @@ char *np_extract_value(const char *varlist, const char *name, char sep) {
         return value;
 }
 
+/*
+ * Replace occurrences of "%m" by strerror(errno).  Other printf(3)-style
+ * conversion specifications will be copied verbatim, including "%%", even if
+ * followed by an "m".  Returns a pointer to a static buffer in order to not
+ * fail on memory allocation error.
+ */
+static char *
+insert_syserr(const char *buf)
+{
+        static char newbuf[8192];
+        char *errstr = strerror(errno);
+        size_t errlen = strlen(errstr);
+        size_t copylen;
+        unsigned i, j;
+
+        for (i = 0, j = 0; buf[i] != '\0' && j < sizeof(newbuf) - 2; i++, j++) {
+                if (buf[i] == '%') {
+                        if (buf[++i] == 'm') {
+                                copylen = (errlen > sizeof(newbuf) - j - 1) ?
+                                    sizeof(newbuf) - j - 1 : errlen;
+                                memcpy(newbuf + j, errstr, copylen);
+                                /*
+                                 * As we'll increment j by 1 after the iteration
+                                 * anyway, we only increment j by the number of
+                                 * copied bytes - 1.
+                                 */
+                                j += copylen - 1;
+                                continue;
+                        } else {
+                                /*
+                                 * The possibility to run into this block is the
+                                 * reason we checked for j < sizeof(newbuf) - 2
+                                 * instead of j < sizeof(newbuf) - 1.
+                                 */
+                                newbuf[j++] = '%';
+                                if (buf[i] == '\0')
+                                        break;
+                        }
+                }
+                newbuf[j] = buf[i];
+        }
+        newbuf[j] = '\0';
+        return newbuf;
+}
+
+/*
+ * Given a numerical status, return a pointer to the according string.
+ */
+const char *
+state_text(int result)
+{
+        switch (result) {
+        case STATE_OK:
+                return "OK";
+        case STATE_WARNING:
+                return "WARNING";
+        case STATE_CRITICAL:
+                return "CRITICAL";
+        case STATE_DEPENDENT:
+                return "DEPENDENT";
+        default:
+                return "UNKNOWN";
+        }
+}
diff --git a/lib/utils_base.h b/lib/utils_base.h
index f40fdb0..8d0b212 100644
--- a/lib/utils_base.h
+++ b/lib/utils_base.h
@@ -37,6 +37,23 @@ int get_status(double, thresholds *);
 
 char *np_escaped_string (const char *);
 
+void np_set_output(const char *, const char *, int, int);
+int np_adjust_verbosity(int);
+void np_debug(int, const char *, ...)
+    __attribute__((format(printf, 2, 3)));
+void np_verbose(const char *, ...)
+    __attribute__((format(printf, 1, 2)));
+void np_die(int, const char *, ...)
+    __attribute__((noreturn, format(printf, 2, 3)));
+
+#define np_verbatim(s) np_verbose("%s", s)
+#define np_increase_verbosity(i) np_adjust_verbosity(i)
+#define np_decrease_verbosity(i) np_adjust_verbosity(-i)
+#define np_get_verbosity() np_adjust_verbosity(0)
+#define np_set_verbosity(v) np_set_output(NULL, NULL, v, 0)
+#define np_set_mynames(p, s) np_set_output(p, s, -2, 0)
+
+/* TODO: die() can be removed as soon as all plugins use np_die() instead. */
 void die (int, const char *, ...) __attribute__((noreturn,format(printf, 2, 3)));
 
 /* Return codes for _set_thresholds */
@@ -64,4 +81,7 @@ char *np_extract_value(const char*, const char*, char);
  */
 #define np_extract_ntpvar(l, n) np_extract_value(l, n, ',')
 
+/* Given a numerical status, return a pointer to the according string. */
+const char *state_text(int);
+
 #endif /* _UTILS_BASE_ */
diff --git a/plugins/utils.c b/plugins/utils.c
index 4537390..91fa671 100644
--- a/plugins/utils.c
+++ b/plugins/utils.c
@@ -147,23 +147,6 @@ print_revision (const char *command_name, const char *revision)
                  command_name, revision, PACKAGE, VERSION);
 }
 
-const char *
-state_text (int result)
-{
-        switch (result) {
-        case STATE_OK:
-                return "OK";
-        case STATE_WARNING:
-                return "WARNING";
-        case STATE_CRITICAL:
-                return "CRITICAL";
-        case STATE_DEPENDENT:
-                return "DEPENDENT";
-        default:
-                return "UNKNOWN";
-        }
-}
-
 void
 timeout_alarm_handler (int signo)
 {
diff --git a/plugins/utils.h b/plugins/utils.h
index d6e9c8f..9912fbf 100644
--- a/plugins/utils.h
+++ b/plugins/utils.h
@@ -92,8 +92,6 @@ void usage4(const char *) __attribute__((noreturn));
 void usage5(void) __attribute__((noreturn));
 void usage_va(const char *fmt, ...) __attribute__((noreturn));
 
-const char *state_text (int);
-
 #define max(a,b) (((a)>(b))?(a):(b))
 #define min(a,b) (((a)<(b))?(a):(b))