diff --git a/documentation/RELEASE_NOTES.md b/documentation/RELEASE_NOTES.md
index 4b3ecc997..b53572b07 100644
--- a/documentation/RELEASE_NOTES.md
+++ b/documentation/RELEASE_NOTES.md
@@ -17,6 +17,16 @@ should also be read to understand what has changed since earlier releases.
 
 <!-- Insert new items immediately below here ... -->
 
+### epicsEnvShow accepts glob pattern
+
+The optional argument to epicsEnvShow can now be a glob pattern.
+
+### New function `epicsStrnGlobMatch()`
+
+The function `epicsStrnGlobMatch(char* str, size_t len, char* pattern)`
+works exactly the same as `epicsStrGlobMatch()` but takes an additional
+length arguments which limits the number of characters of `str` to match.
+
 ### Glob pattern allowed in `var` command
 
 When used with one argument, the `var` command can be used with a glob pattern
diff --git a/modules/libcom/src/misc/epicsString.c b/modules/libcom/src/misc/epicsString.c
index e18d9214a..2933fb48e 100644
--- a/modules/libcom/src/misc/epicsString.c
+++ b/modules/libcom/src/misc/epicsString.c
@@ -259,30 +259,31 @@ size_t epicsStrnLen(const char *s, size_t maxlen)
     return i;
 }
 
-int epicsStrGlobMatch(const char *str, const char *pattern)
+int epicsStrnGlobMatch(const char *str, size_t len, const char *pattern)
 {
-    const char *cp = NULL, *mp = NULL;
+    const char *mp = NULL;
+    size_t cp = 0, i = 0;
 
-    while ((*str) && (*pattern != '*')) {
-        if ((*pattern != *str) && (*pattern != '?'))
+    while ((i < len) && (str[i]) && (*pattern != '*')) {
+        if ((*pattern != str[i]) && (*pattern != '?'))
             return 0;
         pattern++;
-        str++;
+        i++;
     }
-    while (*str) {
+    while ((i < len) && str[i]) {
         if (*pattern == '*') {
             if (!*++pattern)
                 return 1;
             mp = pattern;
-            cp = str+1;
+            cp = i+1;
         }
-        else if ((*pattern == *str) || (*pattern == '?')) {
+        else if ((*pattern == str[i]) || (*pattern == '?')) {
             pattern++;
-            str++;
+            i++;
         }
         else {
             pattern = mp;
-            str = cp++;
+            i = cp++;
         }
     }
     while (*pattern == '*')
@@ -290,6 +291,10 @@ int epicsStrGlobMatch(const char *str, const char *pattern)
     return !*pattern;
 }
 
+int epicsStrGlobMatch(const char *str, const char *pattern) {
+    return epicsStrnGlobMatch(str, (size_t)-1, pattern);
+}
+
 char * epicsStrtok_r(char *s, const char *delim, char **lasts)
 {
    const char *spanp;
diff --git a/modules/libcom/src/misc/epicsString.h b/modules/libcom/src/misc/epicsString.h
index 854b552c6..76cd722cd 100644
--- a/modules/libcom/src/misc/epicsString.h
+++ b/modules/libcom/src/misc/epicsString.h
@@ -36,6 +36,7 @@ LIBCOM_API char * epicsStrnDup(const char *s, size_t len);
 LIBCOM_API int epicsStrPrintEscaped(FILE *fp, const char *s, size_t n);
 #define epicsStrSnPrintEscaped epicsStrnEscapedFromRaw
 LIBCOM_API size_t epicsStrnLen(const char *s, size_t maxlen);
+LIBCOM_API int epicsStrnGlobMatch(const char *str, size_t len, const char *pattern);
 LIBCOM_API int epicsStrGlobMatch(const char *str, const char *pattern);
 LIBCOM_API char * epicsStrtok_r(char *s, const char *delim, char **lasts);
 LIBCOM_API unsigned int epicsStrHash(const char *str, unsigned int seed);
diff --git a/modules/libcom/src/osi/os/WIN32/osdEnv.c b/modules/libcom/src/osi/os/WIN32/osdEnv.c
index adc40b58c..18e66cb6b 100644
--- a/modules/libcom/src/osi/os/WIN32/osdEnv.c
+++ b/modules/libcom/src/osi/os/WIN32/osdEnv.c
@@ -15,11 +15,11 @@
 
 #include <string.h>
 #include <stdlib.h>
-#include <stdio.h>
 #include <ctype.h>
 #include <errno.h>
 
 #include "epicsStdio.h"
+#include "epicsString.h"
 #include "errlog.h"
 #include "envDefs.h"
 #include "osiUnistd.h"
@@ -61,18 +61,10 @@ LIBCOM_API void epicsStdCall epicsEnvUnset (const char *name)
  */
 LIBCOM_API void epicsStdCall epicsEnvShow (const char *name)
 {
-    if (name == NULL) {
-        extern char **environ;
-        char **sp;
+    char **sp;
 
-        for (sp = environ ; (sp != NULL) && (*sp != NULL) ; sp++)
+    for (sp = environ ; (sp != NULL) && (*sp != NULL) ; sp++) {
+        if (!name || epicsStrnGlobMatch(*sp, strchr(*sp, '=') - *sp, name))
             printf ("%s\n", *sp);
     }
-    else {
-        const char *cp = getenv (name);
-        if (cp == NULL)
-            printf ("%s is not an environment variable.\n", name);
-        else
-            printf ("%s=%s\n", name, cp);
-    }
 }
diff --git a/modules/libcom/src/osi/os/default/osdEnv.c b/modules/libcom/src/osi/os/default/osdEnv.c
index 7ece253c7..74b5b8041 100644
--- a/modules/libcom/src/osi/os/default/osdEnv.c
+++ b/modules/libcom/src/osi/os/default/osdEnv.c
@@ -15,11 +15,11 @@
 
 #include <string.h>
 #include <stdlib.h>
-#include <stdio.h>
 #include <ctype.h>
 #include <errno.h>
 
 #include "epicsStdio.h"
+#include "epicsString.h"
 #include "epicsVersion.h"
 #include "errlog.h"
 #include "envDefs.h"
@@ -68,18 +68,11 @@ LIBCOM_API void epicsStdCall epicsEnvUnset (const char *name)
  */
 LIBCOM_API void epicsStdCall epicsEnvShow (const char *name)
 {
-    if (name == NULL) {
-        extern char **environ;
-        char **sp;
+    extern char **environ;
+    char **sp;
 
-        for (sp = environ ; (sp != NULL) && (*sp != NULL) ; sp++)
+    for (sp = environ ; (sp != NULL) && (*sp != NULL) ; sp++) {
+        if (!name || epicsStrnGlobMatch(*sp, strchr(*sp, '=') - *sp, name))
             printf ("%s\n", *sp);
     }
-    else {
-        const char *cp = getenv (name);
-        if (cp == NULL)
-            printf ("%s is not an environment variable.\n", name);
-        else
-            printf ("%s=%s\n", name, cp);
-    }
 }
diff --git a/modules/libcom/src/osi/os/vxWorks/osdEnv.c b/modules/libcom/src/osi/os/vxWorks/osdEnv.c
index d91208f4c..f178e15cf 100644
--- a/modules/libcom/src/osi/os/vxWorks/osdEnv.c
+++ b/modules/libcom/src/osi/os/vxWorks/osdEnv.c
@@ -16,17 +16,18 @@
 /* This is needed for vxWorks 6.8 to prevent an obnoxious compiler warning */
 #define _VSB_CONFIG_FILE <../lib/h/config/vsbConfig.h>
 
-#include <string.h>
 #include <stdlib.h>
-#include <stdio.h>
+#include <string.h>
 #include <ctype.h>
 #include <envLib.h>
 
 #include "epicsFindSymbol.h"
 #include "epicsStdio.h"
+#include "epicsString.h"
 #include "errlog.h"
 #include "iocsh.h"
 
+
 /*
  * Set the value of an environment variable
  * Leaks memory, but the assumption is that this routine won't be
@@ -86,14 +87,12 @@ LIBCOM_API void epicsStdCall epicsEnvUnset (const char *name)
  */
 LIBCOM_API void epicsStdCall epicsEnvShow (const char *name)
 {
-    if (name == NULL) {
-        envShow (0);
-    }
-    else {
-        const char *cp = getenv (name);
-        if (cp == NULL)
-            printf ("%s is not an environment variable.\n", name);
-        else
-            printf ("%s=%s\n", name, cp);
+    extern char **ppGlobalEnviron;
+    char **sp;
+
+    for (sp = environ ; (sp != NULL) && (*sp != NULL) ; sp++) {
+        if (!**sp) continue; /* skip unset environment variables */
+        if (!name || epicsStrnGlobMatch(*sp, strchr(*sp, '=') - *sp, name))
+            printf ("%s\n", *sp);
     }
 }