Com: iocsh: Tab completion

Add tab completion for "help ...", record names, and "pdbbase"
2022-06-20 20:33:56 -07:00
parent 60128ee924
commit d9ca8a70f0
10 changed files with 284 additions and 32 deletions
--- a/modules/database/src/ioc/as/asIocRegister.c
+++ b/modules/database/src/ioc/as/asIocRegister.c
@@ -16,7 +16,7 @@
 #include "asIocRegister.h"

 /* asSetFilename */
-static const iocshArg asSetFilenameArg0 = { "ascf",iocshArgString};
+static const iocshArg asSetFilenameArg0 = { "ascf",iocshArgStringPath};
 static const iocshArg * const asSetFilenameArgs[] = {&asSetFilenameArg0};
 static const iocshFuncDef asSetFilenameFuncDef =
    {"asSetFilename",1,asSetFilenameArgs,
@@ -97,7 +97,7 @@ static void aspmemCallFunc(const iocshArgBuf *args)
 }

 /* astac */
-static const iocshArg astacArg0 = { "recordname",iocshArgString};
+static const iocshArg astacArg0 = { "recordname",iocshArgStringRecord};
 static const iocshArg astacArg1 = { "user",iocshArgString};
 static const iocshArg astacArg2 = { "host",iocshArgString};
 static const iocshArg * const astacArgs[] = {&astacArg0,&astacArg1,&astacArg2};
--- a/modules/database/src/ioc/db/dbIocRegister.c
+++ b/modules/database/src/ioc/db/dbIocRegister.c
@@ -8,10 +8,13 @@
 * in file LICENSE that is included with this distribution.
 \*************************************************************************/

+#define EPICS_PRIVATE_API
+
 #include "iocsh.h"

 #include "callback.h"
 #include "dbAccess.h"
+#include "dbStaticPvt.h"
 #include "dbBkpt.h"
 #include "dbCaTest.h"
 #include "dbEvent.h"
@@ -28,8 +31,8 @@
 DBCORE_API extern int callbackParallelThreadsDefault;

 /* dbLoadDatabase */
-static const iocshArg dbLoadDatabaseArg0 = { "file name",iocshArgString};
-static const iocshArg dbLoadDatabaseArg1 = { "path",iocshArgString};
+static const iocshArg dbLoadDatabaseArg0 = { "file name",iocshArgStringPath};
+static const iocshArg dbLoadDatabaseArg1 = { "path",iocshArgStringPath};
 static const iocshArg dbLoadDatabaseArg2 = { "substitutions",iocshArgString};
 static const iocshArg * const dbLoadDatabaseArgs[3] =
 {
@@ -49,7 +52,7 @@ static void dbLoadDatabaseCallFunc(const iocshArgBuf *args)
 }

 /* dbLoadRecords */
-static const iocshArg dbLoadRecordsArg0 = { "file name",iocshArgString};
+static const iocshArg dbLoadRecordsArg0 = { "file name",iocshArgStringPath};
 static const iocshArg dbLoadRecordsArg1 = { "substitutions",iocshArgString};
 static const iocshArg * const dbLoadRecordsArgs[2] = {&dbLoadRecordsArg0,&dbLoadRecordsArg1};
 static const iocshFuncDef dbLoadRecordsFuncDef = {
@@ -66,28 +69,28 @@ static void dbLoadRecordsCallFunc(const iocshArgBuf *args)
 }

 /* dbb */
-static const iocshArg dbbArg0 = { "record name",iocshArgString};
+static const iocshArg dbbArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbbArgs[1] = {&dbbArg0};
 static const iocshFuncDef dbbFuncDef = {"dbb",1,dbbArgs,
                                        "Add breakpoint to a lock set.\n"};
 static void dbbCallFunc(const iocshArgBuf *args) { dbb(args[0].sval);}

 /* dbd */
-static const iocshArg dbdArg0 = { "record name",iocshArgString};
+static const iocshArg dbdArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbdArgs[1] = {&dbdArg0};
 static const iocshFuncDef dbdFuncDef = {"dbd",1,dbdArgs,
                                        "Remove breakpoint from a record.\n"};
 static void dbdCallFunc(const iocshArgBuf *args) { dbd(args[0].sval);}

 /* dbc */
-static const iocshArg dbcArg0 = { "record name",iocshArgString};
+static const iocshArg dbcArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbcArgs[1] = {&dbcArg0};
 static const iocshFuncDef dbcFuncDef = {"dbc",1,dbcArgs,
                                        "Continue processing in a lock set.\n"};
 static void dbcCallFunc(const iocshArgBuf *args) { dbc(args[0].sval);}

 /* dbs */
-static const iocshArg dbsArg0 = { "record name",iocshArgString};
+static const iocshArg dbsArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbsArgs[1] = {&dbsArg0};
 static const iocshFuncDef dbsFuncDef = {"dbs",1,dbsArgs,
                                        "Step through record processing.\n"};
@@ -99,7 +102,7 @@ static const iocshFuncDef dbstatFuncDef = {"dbstat",0,0,
 static void dbstatCallFunc(const iocshArgBuf *args) { dbstat();}

 /* dbp */
-static const iocshArg dbpArg0 = { "record name",iocshArgString};
+static const iocshArg dbpArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dbpArg1 = { "interest level",iocshArgInt};
 static const iocshArg * const dbpArgs[2] = {&dbpArg0,&dbpArg1};
 static const iocshFuncDef dbpFuncDef = {"dbp",2,dbpArgs,
@@ -108,7 +111,7 @@ static void dbpCallFunc(const iocshArgBuf *args)
 { dbp(args[0].sval,args[1].ival);}

 /* dbap */
-static const iocshArg dbapArg0 = { "record name",iocshArgString};
+static const iocshArg dbapArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbapArgs[1] = {&dbapArg0};
 static const iocshFuncDef dbapFuncDef = {"dbap",1,dbapArgs,
                                         "toggle printing after processing a certain record.\n"};
@@ -122,7 +125,7 @@ static const iocshFuncDef dbsrFuncDef = {"dbsr",1,dbsrArgs,
 static void dbsrCallFunc(const iocshArgBuf *args) { dbsr(args[0].ival);}

 /* dbcar */
-static const iocshArg dbcarArg0 = { "record name",iocshArgString};
+static const iocshArg dbcarArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dbcarArg1 = { "level",iocshArgInt};
 static const iocshArg * const dbcarArgs[2] = {&dbcarArg0,&dbcarArg1};
 static const iocshFuncDef dbcarFuncDef = {"dbcar",2,dbcarArgs,
@@ -137,7 +140,7 @@ static void dbcarCallFunc(const iocshArgBuf *args)
 }

 /* dbjlr */
-static const iocshArg dbjlrArg0 = { "record name",iocshArgString};
+static const iocshArg dbjlrArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dbjlrArg1 = { "level",iocshArgInt};
 static const iocshArg * const dbjlrArgs[2] = {&dbjlrArg0,&dbjlrArg1};
 static const iocshFuncDef dbjlrFuncDef = {"dbjlr",2,dbjlrArgs,
@@ -148,7 +151,7 @@ static void dbjlrCallFunc(const iocshArgBuf *args)
 }

 /* dbel */
-static const iocshArg dbelArg0 = { "record name",iocshArgString};
+static const iocshArg dbelArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dbelArg1 = { "level",iocshArgInt};
 static const iocshArg * const dbelArgs[2] = {&dbelArg0,&dbelArg1};
 static const iocshFuncDef dbelFuncDef = {"dbel",2,dbelArgs,
@@ -160,7 +163,7 @@ static void dbelCallFunc(const iocshArgBuf *args)
 }

 /* dba */
-static const iocshArg dbaArg0 = { "record name",iocshArgString};
+static const iocshArg dbaArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbaArgs[1] = {&dbaArg0};
 static const iocshFuncDef dbaFuncDef = {"dba",1,dbaArgs,
                                        "dbAddr info.\n"};
@@ -194,21 +197,21 @@ static const iocshFuncDef dbliFuncDef = {"dbli",1,dbliArgs,
 static void dbliCallFunc(const iocshArgBuf *args) { dbli(args[0].sval);}

 /* dbla */
-static const iocshArg dblaArg0 = { "pattern",iocshArgString};
+static const iocshArg dblaArg0 = { "pattern",iocshArgStringRecord};
 static const iocshArg * const dblaArgs[1] = {&dblaArg0};
 static const iocshFuncDef dblaFuncDef = {"dbla",1,dblaArgs,
                                         "List record alias()s by alias name pattern.\n"};
 static void dblaCallFunc(const iocshArgBuf *args) { dbla(args[0].sval);}

 /* dbgrep */
-static const iocshArg dbgrepArg0 = { "pattern",iocshArgString};
+static const iocshArg dbgrepArg0 = { "pattern",iocshArgStringRecord};
 static const iocshArg * const dbgrepArgs[1] = {&dbgrepArg0};
 static const iocshFuncDef dbgrepFuncDef = {"dbgrep",1,dbgrepArgs,
                                           "List record names matching pattern.\n"};
 static void dbgrepCallFunc(const iocshArgBuf *args) { dbgrep(args[0].sval);}

 /* dbgf */
-static const iocshArg dbgfArg0 = { "record name",iocshArgString};
+static const iocshArg dbgfArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbgfArgs[1] = {&dbgfArg0};
 static const iocshFuncDef dbgfFuncDef = {"dbgf",1,dbgfArgs,
                                         "Database Get Field.\n"
@@ -216,7 +219,7 @@ static const iocshFuncDef dbgfFuncDef = {"dbgf",1,dbgfArgs,
 static void dbgfCallFunc(const iocshArgBuf *args) { dbgf(args[0].sval);}

 /* dbpf */
-static const iocshArg dbpfArg0 = { "record name",iocshArgString};
+static const iocshArg dbpfArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dbpfArg1 = { "value",iocshArgString};
 static const iocshArg * const dbpfArgs[2] = {&dbpfArg0,&dbpfArg1};
 static const iocshFuncDef dbpfFuncDef = {"dbpf",2,dbpfArgs,
@@ -226,7 +229,7 @@ static void dbpfCallFunc(const iocshArgBuf *args)
 { dbpf(args[0].sval,args[1].sval);}

 /* dbpr */
-static const iocshArg dbprArg0 = { "record name",iocshArgString};
+static const iocshArg dbprArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dbprArg1 = { "interest level",iocshArgInt};
 static const iocshArg * const dbprArgs[2] = {&dbprArg0,&dbprArg1};
 static const iocshFuncDef dbprFuncDef = {"dbpr",2,dbprArgs,
@@ -236,14 +239,14 @@ static void dbprCallFunc(const iocshArgBuf *args)
 { dbpr(args[0].sval,args[1].ival);}

 /* dbtr */
-static const iocshArg dbtrArg0 = { "record name",iocshArgString};
+static const iocshArg dbtrArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbtrArgs[1] = {&dbtrArg0};
 static const iocshFuncDef dbtrFuncDef = {"dbtr",1,dbtrArgs,
                                         "Process record and then some fields.\n"};
 static void dbtrCallFunc(const iocshArgBuf *args) { dbtr(args[0].sval);}

 /* dbtgf */
-static const iocshArg dbtgfArg0 = { "record name",iocshArgString};
+static const iocshArg dbtgfArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const dbtgfArgs[1] = {&dbtgfArg0};
 static const iocshFuncDef dbtgfFuncDef = {"dbtgf",1,dbtgfArgs,
                                          "Database Test Get Field.\n"
@@ -251,7 +254,7 @@ static const iocshFuncDef dbtgfFuncDef = {"dbtgf",1,dbtgfArgs,
 static void dbtgfCallFunc(const iocshArgBuf *args) { dbtgf(args[0].sval);}

 /* dbtpf */
-static const iocshArg dbtpfArg0 = { "record name",iocshArgString};
+static const iocshArg dbtpfArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dbtpfArg1 = { "value",iocshArgString};
 static const iocshArg * const dbtpfArgs[2] = {&dbtpfArg0,&dbtpfArg1};
 static const iocshFuncDef dbtpfFuncDef = {"dbtpf",2,dbtpfArgs,
@@ -274,14 +277,14 @@ static const iocshFuncDef dbhcrFuncDef = {"dbhcr",0,0,
 static void dbhcrCallFunc(const iocshArgBuf *args) { dbhcr();}

 /* gft */
-static const iocshArg gftArg0 = { "record name",iocshArgString};
+static const iocshArg gftArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg * const gftArgs[1] = {&gftArg0};
 static const iocshFuncDef gftFuncDef = {"gft",1,gftArgs,
                                        "Report dbChannel info and value.\n"};
 static void gftCallFunc(const iocshArgBuf *args) { gft(args[0].sval);}

 /* pft */
-static const iocshArg pftArg0 = { "record name",iocshArgString};
+static const iocshArg pftArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg pftArg1 = { "value",iocshArgString};
 static const iocshArg * const pftArgs[2] = {&pftArg0,&pftArg1};
 static const iocshFuncDef pftFuncDef = {"pft",2,pftArgs,
@@ -290,7 +293,7 @@ static void pftCallFunc(const iocshArgBuf *args)
 { pft(args[0].sval,args[1].sval);}

 /* dbtpn */
-static const iocshArg dbtpnArg0 = { "record name",iocshArgString};
+static const iocshArg dbtpnArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dbtpnArg1 = { "value",iocshArgString};
 static const iocshArg * const dbtpnArgs[2] = {&dbtpnArg0,&dbtpnArg1};
 static const iocshFuncDef dbtpnFuncDef = {"dbtpn",2,dbtpnArgs,
@@ -318,7 +321,7 @@ static void dbPutAttrCallFunc(const iocshArgBuf *args)
 { dbPutAttribute(args[0].sval,args[1].sval,args[2].sval);}

 /* tpn */
-static const iocshArg tpnArg0 = { "record name",iocshArgString};
+static const iocshArg tpnArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg tpnArg1 = { "value",iocshArgString};
 static const iocshArg * const tpnArgs[2] = {&tpnArg0,&tpnArg1};
 static const iocshFuncDef tpnFuncDef = {"tpn",2,tpnArgs,
@@ -327,7 +330,7 @@ static void tpnCallFunc(const iocshArgBuf *args)
 { tpn(args[0].sval,args[1].sval);}

 /* dblsr */
-static const iocshArg dblsrArg0 = { "record name",iocshArgString};
+static const iocshArg dblsrArg0 = { "record name",iocshArgStringRecord};
 static const iocshArg dblsrArg1 = { "interest level",iocshArgInt};
 static const iocshArg * const dblsrArgs[2] = {&dblsrArg0,&dblsrArg1};
 static const iocshFuncDef dblsrFuncDef = {"dblsr",2,dblsrArgs,
@@ -500,6 +503,8 @@ static void dbStateShowAllCallFunc (const iocshArgBuf *args)

 void dbIocRegister(void)
 {
+    iocshCompleteRecord = &dbCompleteRecord;
+
    iocshRegister(&dbbFuncDef,dbbCallFunc);
    iocshRegister(&dbdFuncDef,dbdCallFunc);
    iocshRegister(&dbcFuncDef,dbcCallFunc);
--- a/modules/database/src/ioc/dbStatic/Makefile
+++ b/modules/database/src/ioc/dbStatic/Makefile
@@ -28,5 +28,6 @@ dbCore_SRCS += dbYacc.c
 dbCore_SRCS += dbPvdLib.c
 dbCore_SRCS += dbStaticRun.c
 dbCore_SRCS += dbStaticIocRegister.c
+dbCore_SRCS += dbCompleteRecord.cpp

 CLEANS += dbLex.c dbYacc.c
--- a/modules/database/src/ioc/dbStatic/dbCompleteRecord.cpp
+++ b/modules/database/src/ioc/dbStatic/dbCompleteRecord.cpp
@@ -0,0 +1,161 @@
+/*************************************************************************\
+* Copyright (c) 2022 Michael Davidsaver
+* SPDX-License-Identifier: EPICS
+* EPICS Base is distributed subject to a Software License Agreement found
+* in file LICENSE that is included with this distribution.
+\*************************************************************************/
+
+#include <algorithm>
+#include <limits>
+#include <string>
+#include <set>
+
+#include <string.h>
+
+#include <epicsStdio.h>
+#include <dbAccess.h>
+#include "dbStaticPvt.h"
+
+namespace {
+
+// immutable C string slice.  (avoid allocating many temporary std::string)
+class CStr {
+    const char* p;
+    size_t l;
+public:
+    CStr() :p(NULL), l(0u) {}
+    CStr(const CStr& o) :p(o.p), l(o.l) {}
+    explicit CStr(const char* p) :p(p), l(p ? strlen(p) : 0u) {}
+    CStr(const char* p, size_t n) :p(p), l(n) {}
+
+    CStr& operator=(const CStr& o) {
+        p = o.p;
+        l = o.l;
+        return *this;
+    }
+
+    bool operator==(const CStr& o) const {
+        return l==o.l && (p==o.p || memcmp(p, o.p, l)==0);
+    }
+    bool operator!=(const CStr& o) const {
+        return !(*this==o);
+    }
+    bool operator<(const CStr& o) const {
+        size_t pl = std::min(l, o.l);
+        int cmp = memcmp(p, o.p, pl);
+        return cmp<0 || (cmp==0 && l < o.l);
+    }
+
+    bool empty() const { return !l; }
+    size_t size() const { return l; }
+
+    bool prefixOf(const CStr& full) const {
+        return full.l >= l && memcmp(full.p, p, l)==0;
+    }
+
+    CStr commonPrefix(const CStr& o, size_t startFrom=0u) const {
+        size_t n, N;
+        for(n=startFrom, N=std::min(l, o.l); n<N; n++) {
+            if(p[n]!=o.p[n])
+                break;
+        }
+        return CStr(p, n);
+    }
+
+    void chop_at_first_of(const char* sep, size_t startFrom=0u) {
+        size_t n;
+        for(n=startFrom; n<l; n++) {
+            char c = p[n];
+            for(const char *s = sep; *s; s++) {
+                if(c == *s) {
+                    l = n+1u; // include trailing separator
+                    return;
+                }
+            }
+        }
+    }
+
+    char* dup() const {
+        char* ret = (char*)malloc(l+1u);
+        if(ret) {
+            memcpy(ret, p, l);
+            ret[l] = '\0';
+        }
+        return ret;
+    }
+};
+
+} // namespace
+
+char** dbCompleteRecord(const char *cword)
+{
+    const CStr word(cword);
+
+    DBENTRY ent;
+
+    dbInitEntry(pdbbase, &ent);
+    try{
+        // iterating all record twice...
+
+        CStr prefix;
+        bool first = true;
+
+        // find longest prefix match
+        for(long status = dbFirstRecordType(&ent); !status; status = dbNextRecordType(&ent)) {
+            for(status = dbFirstRecord(&ent); !status; status = dbNextRecord(&ent)) {
+                const CStr name(ent.precnode->recordname);
+
+                if(!word.prefixOf(name))
+                    continue;
+
+                if(first) { // first match
+                    prefix = name;
+                    first = false;
+
+                } else {
+                    prefix = prefix.commonPrefix(name, word.size());
+                }
+            }
+        }
+
+        // with prefix size known, iterate again to find suggestions
+        typedef std::set<CStr> suggestions_t;
+        suggestions_t suggestions;
+
+        for(long status = dbFirstRecordType(&ent); !status; status = dbNextRecordType(&ent)) {
+            for(status = dbFirstRecord(&ent); !status; status = dbNextRecord(&ent)) {
+                CStr name(ent.precnode->recordname);
+
+                if(!prefix.prefixOf(name))
+                    continue;
+
+                name.chop_at_first_of(":<>{}-", prefix.size());
+                suggestions.insert(name);
+            }
+        }
+
+        dbFinishEntry(&ent);
+
+        char** ret = NULL;
+
+        if(!prefix.empty() || !suggestions.empty()) {
+            ret = (char**)malloc(sizeof(*ret)*(2u + suggestions.size()));
+            ret[0] = prefix.dup();
+            size_t n=1u;
+            for(suggestions_t::iterator it(suggestions.begin()), end(suggestions.end());
+                it!=end; ++it)
+            {
+                ret[n++] = it->dup();
+            }
+            ret[n] = NULL;
+        }
+
+        return ret;
+
+    } catch(std::exception& e){
+        fprintf(stderr, "dbCompleteRecord error: %s\n", e.what());
+        dbFinishEntry(&ent);
+        return NULL;
+    }
+
+}
--- a/modules/database/src/ioc/dbStatic/dbStaticPvt.h
+++ b/modules/database/src/ioc/dbStatic/dbStaticPvt.h
@@ -115,6 +115,9 @@ PVDENTRY *dbPvdAdd(DBBASE *pdbbase,dbRecordType *precordType,dbRecordNode *precn
 void dbPvdDelete(DBBASE *pdbbase,dbRecordNode *precnode);
 void dbPvdFreeMem(DBBASE *pdbbase);

+DBCORE_API
+char** dbCompleteRecord(const char *word);
+
 #ifdef __cplusplus
 }
 #endif
--- a/modules/database/src/ioc/dbtemplate/dbtoolsIocRegister.c
+++ b/modules/database/src/ioc/dbtemplate/dbtoolsIocRegister.c
@@ -13,7 +13,7 @@


 /* dbLoadTemplate */
-static const iocshArg dbLoadTemplateArg0 = {"filename", iocshArgString};
+static const iocshArg dbLoadTemplateArg0 = {"filename", iocshArgStringPath};
 static const iocshArg dbLoadTemplateArg1 = {"var1=value1,var2=value2", iocshArgString};
 static const iocshArg * const dbLoadTemplateArgs[2] = {
    &dbLoadTemplateArg0, &dbLoadTemplateArg1
--- a/modules/database/src/ioc/misc/dlload.c
+++ b/modules/database/src/ioc/misc/dlload.c
@@ -17,7 +17,7 @@ IOCSH_STATIC_FUNC void dlload(const char* name)
    }
 }

-static const iocshArg dlloadArg0 = { "path/library.so", iocshArgString};
+static const iocshArg dlloadArg0 = { "path/library.so", iocshArgStringPath};
 static const iocshArg * const dlloadArgs[] = {&dlloadArg0};
 static const iocshFuncDef dlloadFuncDef = {
    "dlload",
--- a/modules/libcom/src/iocsh/iocsh.cpp
+++ b/modules/libcom/src/iocsh/iocsh.cpp
@@ -23,6 +23,8 @@
 #include <ctype.h>
 #include <errno.h>

+#define EPICS_PRIVATE_API
+
 #include "epicsMath.h"
 #include "errlog.h"
 #include "macLib.h"
@@ -216,6 +218,8 @@ showError (const char *filename, int lineno, const char *msg, ...)
    va_end (ap);
 }

+char** (*iocshCompleteRecord)(const char *word) = NULL;
+
 namespace {

 struct Tokenize {
@@ -495,6 +499,74 @@ char** iocsh_attempt_completion(const char* word, int start, int end)
        return rl_completion_matches(word, iocsh_complete_command);

    } else { // complete some argument
+        // make a copy as split() will insert nils
+        size_t linelen = strlen(line);
+        std::vector<char> lbuf(linelen+1u);
+        memcpy(&lbuf[0], line, linelen);
+        lbuf[linelen] = '\0';
+
+        int pos = 0;
+        while(isspace(lbuf[pos]))
+            pos++;
+
+        Tokenize tokenize;
+        // don't complain about "Unbalanced quote when completing
+        tokenize.noise = false;
+        bool err = tokenize.split(NULL, -1, &lbuf[0], pos);
+
+        if(!err)
+            err = tokenize.empty() && tokenize.redirects.empty();
+
+        // look up command name
+        iocshCmdDef *def = NULL;
+        if(!err)
+            err = !(def = (iocshCmdDef *) registryFind(iocshCmdID, tokenize.argv[0]));
+
+        // Find out which argument 'start' is.
+        // arg is index into tokenize.argv[]
+        // argv[0] is command name, argv[1] would be first argument.
+        size_t arg;
+        if(!err) {
+            for(arg=1; arg<tokenize.size(); arg++) {
+                // BUG: does not work with eg. 'dbpr("X")' as split()
+                //      has rewritten lbuf to make this 'dbpr "X"'
+                size_t soffset = tokenize.argv[arg]-&lbuf[0];
+                size_t eoffset = soffset + strlen(tokenize.argv[arg]);
+                if(soffset >= size_t(start) && eoffset <= size_t(end)) {
+                    break;
+                }
+            }
+            err = arg-1u >= size_t(def->pFuncDef->nargs);
+        }
+
+        if(!err) {
+            // we are being asked to complete a valid command,
+            // for which we have split argument strings.
+
+            const iocshArg * argdef = def->pFuncDef->arg[arg-1u];
+
+            // known argument type
+            rl_attempted_completion_over = 1;
+
+            if(argdef->type==iocshArgStringRecord && iocshCompleteRecord) {
+                return (*iocshCompleteRecord)(word);
+
+            } else if(argdef->type==iocshArgStringPath) {
+                // use default completion (filesystem)
+                rl_attempted_completion_over = 0;
+
+            } else if(argdef->type==iocshArgPdbbase) {
+                char **ret = (char**)calloc(2, sizeof(*ret));
+                if(ret)
+                    ret[0] = strdup("pdbbase");
+                return ret;
+
+            } else if(arg==1 && strcmp(def->pFuncDef->name, "help")==0) {
+                return rl_completion_matches(word, iocsh_complete_command);
+            }
+
+        }
+
        return NULL;
    }
 }
@@ -701,6 +773,8 @@ cvtArg (const char *filename, int lineno, char *arg, iocshArgBuf *argBuf,
        break;

    case iocshArgString:
+    case iocshArgStringRecord:
+    case iocshArgStringPath:
        argBuf->sval = arg;
        break;

--- a/modules/libcom/src/iocsh/iocsh.h
+++ b/modules/libcom/src/iocsh/iocsh.h
@@ -65,7 +65,9 @@ typedef enum {
    iocshArgString,
    iocshArgPdbbase,
    iocshArgArgv,
-    iocshArgPersistentString
+    iocshArgPersistentString,
+    iocshArgStringRecord,
+    iocshArgStringPath,
 }iocshArgType;

 /**
@@ -297,6 +299,12 @@ LIBCOM_API void epicsStdCall iocshEnvClear(const char *name);
 /* 'weak' link to pdbbase */
 LIBCOM_API extern struct dbBase **iocshPpdbbase;

+#ifdef EPICS_PRIVATE_API
+
+LIBCOM_API
+extern char** (*iocshCompleteRecord)(const char *word);
+#endif
+
 #ifdef __cplusplus
 }
 #endif
--- a/modules/libcom/src/iocsh/libComRegister.c
+++ b/modules/libcom/src/iocsh/libComRegister.c
@@ -98,7 +98,7 @@ static void echoCallFunc(const iocshArgBuf *args)
 }

 /* chdir */
-static const iocshArg chdirArg0 = { "directory name",iocshArgString};
+static const iocshArg chdirArg0 = { "directory name",iocshArgStringPath};
 static const iocshArg * const chdirArgs[1] = {&chdirArg0};
 static const iocshFuncDef chdirFuncDef = {"cd",1,chdirArgs,
                                          "Change directory to new directory provided as parameter\n"};