Strings on an ESP8266

Projects Programming
1

I am new to C++ and the following is a routine I wrote to format a command defined as string MDCommand:

</>
void formatMDCommand(char * inputstring) {

char * Command = "";
char * field1 = "";
char * field2 = "";
char * field3 = "";
char * field4 = "";
char * field5 = "";
char * field6 = "";
char * field7 = "";
char * field8 = "";
char * field9 = "";
char * field10 = "";

#if debug
Serial.println("Formatting MD Command: ");
Serial.println("inputstring: [" + String(inputstring));
Serial.println("Delimiters: [" + String(commandDelimeters));
#endif

Command = strtok(inputstring,commandDelimeters); // get the command
MDCommand = "MD";

field1 = strtok(NULL, commandDelimeters); // get the parameter if any
field2 = strtok(NULL, commandDelimeters); // get the parameter if any
field3 = strtok(NULL, commandDelimeters); // get the parameter if any
field4 = strtok(NULL, commandDelimeters); // get the parameter if any

#if debug
Serial.println("Formatting MD Command: ");
Serial.println("field1: [" + String(field1) + "]");
Serial.println("field2: [" + String(field2) + "]");
Serial.println("field3: [" + String(field3) + "]");
Serial.println("field4: [" + String(field4) + "]");
#endif

if (field1!= "") {
MDCommand = "MD" + char(9) + String(field1);
Serial.println(MDCommand);
}
if (field2 != "") {
MDCommand = "MD" + char(9) + String(field1) + char(9) + String(field2);
Serial.println(MDCommand);
}
if (field3 != "") {
MDCommand = "MD" + char(9) + String(field1) + char(9) + String(field2) + char(9) + String(field3);
Serial.println(MDCommand);
}
if (field4 != "") {
MDCommand = "MD" + char(9) + String(field1) + char(9) + String(field2) + char(9) + String(field3) + char(9) + String(field4);
Serial.println(MDCommand);
}
#if debug
Serial.println("MD Command: [" + MDCommand + "]");
#endif
}
</>

This is what I am getting on the Serial Monitor for debugging:

Formatting MD Command:
inputstring: [795631813456 MEXICO 5/25/2019 A10012345 $⸮?⸮$⸮?
Delimiters: [|
Formatting MD Command:
field1: [MEXICO]
field2: [5/25/2019]
field3: [A10012345]
field4: [$⸮?⸮$⸮?]
1: [MEXICO
1: [MEXICO 5/25/2019
1: [MEXICO 5/25/2019 A10012345
1: [MEXICO 5/25/2019 A10012345 $⸮?⸮$⸮?
MD Command: [1: [MEXICO 5/25/2019 A10012345 $⸮?⸮$⸮?]

I don’t get why it is not formatting the “MD” at the beginning of the command. It should have been “MD{tab}MEXICO{tab}05/25/2019{tab}A10012345

It's like something is stepping on variable memory. When I compile I have the following memory left

Archiving built core (caching) in: C:\Users\Randy\AppData\Local\Temp\arduino_cache_251239\core\core_esp8266_esp8266_nodemcuv2_CpuFrequency_80,FlashSize_4M1M,LwIPVariant_v2mss536,Debug_Serial,DebugLevel_None____,FlashErase_none,UploadSpeed_115200_0b29be32429285d6ae765e2f856d5e55.a
Sketch uses 296856 bytes (28%) of program storage space. Maximum is 1044464 bytes.
Global variables use 49092 bytes (59%) of dynamic memory, leaving 32828 bytes for local variables. Maximum is 81920 bytes.

So looks like I have plenty of space.

2

make sure to format your code correctly using the </> symbol at the top so your code is easier to read

3

Maybe your inputString has not been null terminated.

4

I went and appended '\0' to the end of inputstring and now I get this on Serial Monitor. It did clean up the end of the input string.

Do I need to add '\0' to the strtok command when extracting the individual fields? or does strtok take care of that?

Formatting MD Command:
inputstring: [795631813456 MEXICO 5/25/2019 A10012345
Delimiters: [|
Formatting MD Command:
field1: [MEXICO]
field2: [5/25/2019]
field3: [A10012345]
]
field5: []
field6: []
field7: []
field8: []
field9: []
field10: []
1: [MEXICO
1: [MEXICO 5/25/2019
1: [MEXICO 5/25/2019 A10012345

]

5

Everything cstring needs to be null terminated of you want to use cstring functions on them.

For strtok(), the first argument is a cstring but the second one needs not to be.

6

Ok, sorry new to C++ so my command is char * and the sub fields 1 thru 10 are char * also.

Are you saying the command should be string? Not sure what you mean by cstring.

7

cstring just means that the string is (or needs to be) null terminated.

So the yes, the "command" should be cstring to be used as first argument of strtok ()

8

I need to clarify that "string" in the above post refers to array of chatacters.

9

Anyone know why this does not work?

if (field1!= "") {
MDCommand = "MD" + '\t' + field1;
Serial.println(MDCommand);
}

What I get on the serial monitor is:

Formatting MD Command:
inputstring: [795631813456 MEXICO 5/25/2019 A10012345
Delimiters: [|
Formatting MD Command:
field1: [MEXICO]
field2: [5/25/2019]
field3: [A10012345]

Following is the result of the Serial.println(MDCommand);

1: [MEXICO

Why does not display MD MEXICO?

field1 is defined as string field1;