Change require PV prefix to use defined IOC name

Uses IOCNAME environment variable value if this is defined. This
makes the require PVs persistent across IOC restarts. Falls back
to the original definition of hostname and PID if the IOCNAME
environment variable is not defined.

tools/iocsh_functions

@@ -277,7 +277,7 @@ function iocsh_ps1
     iocsh_ps1+="-";
     iocsh_ps1+=$pid;
     iocsh_ps1+=" > ";
-    
+
     echo "${iocsh_ps1}"
 };
 
@@ -302,17 +302,23 @@ function require_ioc
     #  #define PVNAME_STRINGSZ 61 in EPICS_BASE/include/dbDefs.h
 
     local require_ioc=""
-    local pid="$1";
-    # Keep only short hostname (without domain)
-    local hostname=${HOSTNAME%%.*};
-    # Record name should not have . character, because it is used inside reacord
-
-    require_ioc="REQMOD";          # char 6  ( 6)
-    require_ioc+=":";              # char 1  ( 7)  
-    require_ioc+=${hostname:0:15}; # char 15 (22)
-    require_ioc+="-";              # char 1  (23)
-    require_ioc+=${pid}            # char 7  (30),  max pid in  64 bit  4194304 (7),
-  
+
+    # Test if IOCNAME is defined
+    if [ -z "${IOCNAME}" ]; then
+        local pid="$1";
+        # Keep only short hostname (without domain)
+        local hostname=${HOSTNAME%%.*};
+        # Record name should not have . character, because it is used inside reacord
+
+        require_ioc="REQMOD";          # char 6  ( 6)
+        require_ioc+=":";              # char 1  ( 7)  
+        require_ioc+=${hostname:0:15}; # char 15 (22)
+        require_ioc+="-";              # char 1  (23)
+        require_ioc+=${pid};           # char 7  (30),  max pid in  64 bit  4194304 (7),
+    else
+        require_ioc=${IOCNAME:0:30};
+    fi
+
     echo "${require_ioc}"
 };