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Can someone help me to understand how i need to send the parameters to the function "lora_rf_config" ? Thank you so much !
I try with:
char cfgred[7][10]={'lora_rf_config','915000000','10','0','1','8','14'};
lora_rf_config(7,&cfgred);
The function that im trying to use is:
static void lora_rf_config(int argc, char *argv[])
{
if (argc == 1) {
e_printf("OK%d,%d,%d,%d,%d,%d\r\n", g_lora_config.lorap2p_param.Frequency,
g_lora_config.lorap2p_param.Spreadfact,
g_lora_config.lorap2p_param.Bandwidth,
g_lora_config.lorap2p_param.Codingrate,
g_lora_config.lorap2p_param.Preamlen,
g_lora_config.lorap2p_param.Powerdbm );
return;
} else {
if (argc != 7) {
out_error(RAK_ARG_ERR);
return;
}
if (!(CHECK_P2P_FREQ(atoi(argv[1])) &&
CHECK_P2P_SF(atoi(argv[2])) &&
CHECK_P2P_BDW(atoi(argv[3])) &&
CHECK_P2P_CR(atoi(argv[4])) &&
CHECK_P2P_PREMLEN(atoi(argv[5])) &&
CHECK_P2P_PWR(atoi(argv[6])))) {
out_error(RAK_ARG_ERR);
return;
}
if (read_partition(PARTITION_0, (char *)&g_lora_config, sizeof(g_lora_config)) < 0) {
out_error(RAK_RD_CFG_ERR);
return;
}
g_lora_config.lorap2p_param.Frequency = atoi(argv[1]);
g_lora_config.lorap2p_param.Spreadfact = atoi(argv[2]);
g_lora_config.lorap2p_param.Bandwidth = atoi(argv[3]);
g_lora_config.lorap2p_param.Codingrate = atoi(argv[4]);
g_lora_config.lorap2p_param.Preamlen = atoi(argv[5]);
g_lora_config.lorap2p_param.Powerdbm = atoi(argv[6]);
write_partition(PARTITION_0, (char *)&g_lora_config, sizeof(g_lora_config));
e_printf("OK\r\n");
}
return;
}
The error that i got is:
..\..\..\src\application\RAK811\app.c(107): error: #26: too many characters in character constant
char cfgred[7][10]={'lora_rf_config','915000000','10','0','1','8','14'};
I dont have experience with this kind of arguments.
Thank you for your time.
lora_rf_config expects same arguments than main function: array of pointers to strings, and its length.
Strings in C are pointers to char, where the char buffer they point to has terminating NUL character (if NUL char is missing, then it's not a string, just a character array). In other words, there is no string type in C, but stringiness is determined by the actual data in the char array or buffer. Using "" string literal creates a string, IOW it adds that terminating NUL char in addition to what you write.
// cfgred is array([) of 7 pointers(*) to char.
// Note: string literals are read-only, so you must not modify these
// strings. If you want a modifiable string, this would be a bit more complex,
// but I think this is out of the scope of your question.
char *cfgred[7] = { "lora_rf_config" , "915000000", "10","0", "1", "8", "14"};
// you can get the number of elements in array by dividing its sizeof size (bytes)
// with the size of it's elements in bytes. Just make sure cfgred here is array...
// in the function it is pointer already (arrays get converted to pointers, so
// you can't do this inside the function, you have to do it where you still have
// the original array
int cfgred_len = sizeof cfgred / sizeof(cfgred[0]);
// when you pass array to function, it is automatically converted to pointer,
// so you must not use & when passing an array like this, otherwise types don't
// match
lora_rf_config(cfgred_len, cfgred);
As a side note, always turn on compiler warnings... They help you a lot, fix them. For gcc and clagn, use -Wall -Wextra, for Visual Studio use /W3 or prefereably /W4. And then fix any warnings you get, because they are probably something that doesn't do what you expect.
Your initialization is not done correctly, try changing
char cfgred[7][10]={'lora_rf_config','915000000','10','0','1','8','14'};
into
char cfgred[7][16]={"lora_rf_config","915000000","10","0","1","8","14"};
I am working with FastCgi, trying to generate a dynamic html webpage.
I am able to get the QUERY_STRING easily enough, but I am having trouble trying to copy it into a char array.
If there is even a shorter way of just getting the value from QUERY_STRING, please advise because I am a little over my head.
char *queryString = getenv(ENV_VARS[7]);
char newDeviceName[64];
strncpy( newDeviceName, *queryString, sizeof(*queryString) -1);
printf("------- %c ------------", newDeviceName);
This compiles with only warnings, but once i try to load the webpage, the characters are some weird Chinese looking characters. -> �ፙ�
Thank you in advance.
EDIT: More of my code
const char *ENV_VARS[] = {
"DOCUMENT_ROOT",
"HTTP_COOKIE",
"HTTP_HOST",
"HTTP_REFERER",
"HTTP_USER_AGENT",
"HTTPS",
"PATH",
"QUERY_STRING",
"REMOTE_ADDR",
"REMOTE_HOST",
"REMOTE_PORT",
"REMOTE_USER",
"REQUEST_METHOD",
"REQUEST_URI",
"SCRIPT_FILENAME",
"SCRIPT_NAME",
"SERVER_ADMIN",
"SERVER_NAME",
"SERVER_PORT",
"SERVER_SOFTWARE"
};
int main(void)
{
char deviceName[]=ADAPTERNAME;
time_t t;
/* Intializes random number generator */
srand((unsigned) time(&t));
while (FCGI_Accept() >= 0) {
printf("Content-type: text/html \r\n\r\n");
printf("");
printf("<html>\n");
printf("<script src=\"/js/scripts.js\"></script>");
/* CODE CODE CODE */
printf("<p> hi </p>");
printf("<p> hi </p>");
char *queryString = getenv(ENV_VARS[7]);
char newDeviceName[64];
if (queryString == NULL)
printf("<p> +++++ERROR++++++ </p>");
else {
strcpy( newDeviceName, queryString);
newDeviceName[sizeof(newDeviceName) - 1] = 0;
printf("<p> ------- %s ------------ </p> ", newDeviceName);
}
SOLVED: Amateur mistake, for some reason none of my new edits went into effect until after i restart my lighttpd server.
Your program has undefined behavior. Read those warnings issued by the compiler. They're important.
Don't dereference the pointer when you're passing the string to strncpy(). When you do that, you're now passing a single char. That's converted to a pointer when it's given to strncpy() (which is where you probably get your warning, i.e. passing a char to a function that expects a char*).
You also can't get the size of an array that has decayed to a pointer using sizeof. You're just getting the size of the pointer (which is probably either 8 or 4 bytes depending on your system). Since you don't know the length of the string anyway, it might even be better to just use strcpy() instead of strncpy().
Here's what your code probably should look like:
char *queryString = getenv(ENV_VARS[7]);
char newDeviceName[64];
strcpy( newDeviceName, queryString);
printf("------- %s ------------", newDeviceName); /* use %s to print strings */
The length on your strncpy is wrong [too short], the second argument is wrong, and the format string is incorrect.
Try this:
strncpy( newDeviceName, queryString, sizeof(newDeviceName) - 1);
newDeviceName[sizeof(newDeviceName) - 1] = 0;
printf("------- %s ------------", newDeviceName);
In the call to strncpy, it expects a char * for the second argument, but you pass it a char.
Also, the size is not correct. *queryString is a char and has size 1. Using sizeof(queryString) is not correct either because it will return the size of a pointer. What you actually want is the size of the detination buffer.
In the printf call the %c format specifier expects a char but you pass it a char *. You should instead use %s which expects a char * pointing to a null terminated string.
So what you want to do is this:
strncpy( newDeviceName, queryString, sizeof(newDeviceName) -1);
newDeviceName[sizeof(newDeviceName) - 1] = 0;
printf("------- %s ------------", newDeviceName);
What you want is
strncpy(newDeviceName, queryString, sizeof(newDeviceName)-1);
newDeviceName[63] = '\0'; // Guarantee NUL terminator
printf("----- %s -----", newDeviceName);
So multiple problems:
*queryString just gets you the first character, which strncpy tries to treat as a pointer.
sizeof(*queryString) is the size of a char (i.e. 1)
%c prints a single character, not the string
I used mysql connector and extract data from Database in visual studio 2010. Also inserted data successfully as value. But was fail to insert data with variable. Need a help, please.
this one worked.
mysql_query(connect,"INSERT INTO input VALUES(111,'Bangladesh','Khulna','Male','Muhammad Ashikuzzaman KUET','b+')");
But this are not working.
str="Muhammad Ashikuzzaman KUET";
mysql_query(connect,"INSERT INTO input VALUES(111,'Bangladesh','Khulna','Male','#str','b+')");
or
mysql_query(connect,"INSERT INTO input VALUES(111,'Bangladesh','Khulna','Male',#str,'b+')");
Please suggest a solution.
You have to create the string before calling mysql_query():
char statement[512], *str = "Muhammad Ashikuzzaman KUET";
snprintf(statement, sizeof statement, "INSERT INTO input VALUES(111,'Bangladesh','Khulna','Male','%s','b+')", str);
mysql_query(connect, statement);
Also, be careful when creating those query strings. Don't use functions like sprintf() if you cannot be sure how long the resulting string is. Don't write over the boundaries of the memory segment.
Edit
For precaution, You can use mysql_real_escape_string() additionally if the string usually comes from arbitrary sources:
int insertData(MYSQL *connect, char *str, int str_len) {
if (str_len < 0) {
str_len = strlen(str);
}
char esc[2 * str_len + 1];
unsigned long esclen = mysql_real_escape_string(connect, esc, str, str_len);
char statement[512];
snprintf(statement, sizeof statement, "INSERT INTO input VALUES(111,'Bangladesh','Khulna','Male','%s','b+')", esc);
return mysql_query(connect, statement);
}
Also here I've assumed your input string is small enough to fit into 512 characters string. Practically, it won't work. So declare statement length variable according to input string length plus some extra length to fit with the query string together.
I'm trying to store results taken from a MySQL query into an array of structs. I can't seem to get the types to work though, and I've found the MySQL documentation difficult to sort through.
My struct is:
struct login_session
{
char* user[10];
time_t time;
int length;
};
And the loop where I'm trying to get the data is:
while ( (row = mysql_fetch_row(res)) != NULL ) {
strcpy(records[cnt].user, &row[0]);
cnt++;
}
No matter what I try though I constantly get the error:
test.c:45: warning: passing argument 1 of ‘strcpy’ from incompatible pointer type
/usr/include/string.h:128: note: expected ‘char * __restrict__’ but argument is of type ‘char **’
test.c:45: warning: passing argument 2 of ‘strcpy’ from incompatible pointer type
/usr/include/string.h:128: note: expected ‘const char * __restrict__’ but argument is of type ‘MYSQL_ROW’
Any pointers?
Multiple problems, all related to pointers and arrays, I recommend you do some reading.
First, char * user[10] is defining an array of 10 char * values, not an array of char, which is was I suspect you want. The warning even says as much, strcpy() expects a char *, the user field on its own is seen as a char **.
Second, you're one & away from what you want in the second argument.
Copied from mysql.h header:
typedef char **MYSQL_ROW; /* return data as array of strings */
A MYSQL_ROW is an array of char arrays. Using [] does a dereference, so you dereference down to a char * which is what strcpy() takes, but then you take the address of it using &.
Your code should look more like this:
struct login_session
{
char user[10];
time_t time;
int length;
};
while ( (row = mysql_fetch_row(res)) != NULL ) {
strcpy(records[cnt].user, row[0]);
cnt++;
}
I don't know what guarantees you have about the data coming from mysql, but if you can't be absolutely sure that the rows are <= 10 characters long and null ('\0') terminated, you should use strncpy() to avoid any possibility of overflowing the user array.
I am making an html webpage that uses cgi to access a table/database in mysql. I input a .csv file containing info on my class schedule and the html displays it in the usual schedule table.
My problem is that I can't seem to use strcmp in my parsing cgi as it causes a server error. here is an excerpt of my code where I uses strcmp.
void parse2(char *queu)
{
//---------------------------------------------------------------
char *saveptr[1024];
char *subtoken;
char *Subject;
char *Day;
char *Start;
char *End;
char *Room;
char *Teacher;
int check = 1;
//---------------------------------------------------------------
subtoken = strtok_r(queu, ",", saveptr);
check = strcmp(subtoken, "\0");
printf("%d<br>", check);
if(check == 0){
printf("Error!");
} else {
Subject = subtoken;
Day = strtok_r(NULL, ",", saveptr);
Start = strtok_r(NULL, ",", saveptr);
End = strtok_r(NULL, ",", saveptr);
Room = strtok_r(NULL, ",", saveptr);
Teacher = strtok_r(NULL, ",", saveptr);
printf("%s\n<br/>%s\n<br/>%s\n<br/>%s\n<br/>%s\n<br/>%s\n", Subject, Day, Start, End, Room, Teacher);
//inputsql(Subject, Day, Start, End, Room, Teacher);
}
//---------------------------------------------------------------
}
Note that, I have tested this code and it works fine without me calling strcmp().
I am using strcmp() to prevent a line of unwanted characters, generated after the info when retrieved using POST method, from being entered into my database.
As you can see from the above code, I used strtok() to parse the line of info. Since the line of unwanted characters do not contain a comma (which is my delimiter) it should return a NULL value. correct?
Can anyone help me out? I welcome suggestions to use a different way on solving the problem I chose to solve using strcmp().
I think you should be checking subtoken == NULL, not strcmp(subtoken, "\0") == 0.
"\0" is a string containing a NUL byte, then another NUL (the terminator), so the standard library's string functions will just see an empty string. That's different to a NULL pointer (i.e. a pointer with value zero).
From STRTOK(3):
Each call to strtok() returns a pointer to a null-terminated string
containing the next token. This string does not include the
delimiting byte. If no more tokens are found, strtok() returns NULL.