Sscanf hex to int I have done the following: #include &lt;stdio. Example 1: Using strtol Function In this example, we will use the standard library function strtol to convert the string to a long integer with base 16 and check whether the conversion consumed the entire string, indicating a valid hexadecimal number. Jul 31, 2021 · return(0); } This program generates no output because the $ character required by the sscanf () format string is missing in the value string. Sep 10, 2023 · Note that some implementations of std::sscanf involve a call to std::strlen, which makes their runtime linear on the length of the entire string. If the type is narrower than int, the promoted argument is converted back to the specified type. h> int sscanf(const char *restrict str, const char *restrict format, ); #include <stdarg. When it comes to working with scanf/printf format specifiers, you may want to use the defines from inttypes. Any ideas are much appreciated! Dec 12, 2018 · — str. #include <stdio. Jan 1, 2024 · A white-space character causes the fscanf, scanf, and sscanf functions to read, but not store, all consecutive white-space characters in the input up to the next character that is not a white-space character. NOTE—These ASCII conversion functions return a 32-bit integer value So, the result of the following: string a = "F"; Understand what scanf() is in C Language, its syntax, and how to use it effectively with examples. Aug 7, 2023 · What Is the sscanf() C Function In the C programming language, the sscanf() function lets you read data from a string, similar to how you might read data from standard input (stdin) using the scanf() function. 1. 2 I mportance: P2 normal Target Milestone: --- Assignee: GOTO Masanori URL Jul 24, 2021 · #include <stdint. Dec 10, 2023 · This tutorial will discuss reading formatted data from a character array or string using the sscanf() function in Arduino. Apr 6, 2025 · Learn string parsing in C with this comprehensive sscanf tutorial. Jan 19, 2022 · Hi What are your elegant suggestions for converting a String of hex values into an array of uint8_t? The string of hex can be either of the below (your choice), and the number of hex values can vary. I am trying to read a hex color code from the serial port and convert it to R, G, B values to send to a full color LED. substring(a, b) returning a 12-char String representing a mac- May 28, 2024 · Reading data from files in SystemVerilog involves using tasks like fgetc, ungetc, fgets, fscanf, sscanf, and fread. The C language provides a number of format specifiers that are associated with the different data types such as %d for int, %c for char Conversion specifications which are introduced by the percent sign (%) or the sequence (%n$) where n is a decimal integer in the range [1,NL_ARGMAX]. For sscanf(), the function has to parse the format string, and then decode an integer. C – Read Integer using Scanf () To read an integer entered by user via standard input in C language, use scanf () function. For example, if 00:05:C4:7B is parsed to variables a,b,c,d then the order-corrected sum of the values is: unsigned value = a<<24 + b<<16 + c<<8 + d; where “<<X” is “left shift by X bits” which is the same as multiplying by 2 to the X power. This means there is a single code for most integers and one for most floating point types. h> #include <stdio. %x: Reads a hexadecimal integer. Each argument must be a pointer to a variable with a type that corresponds to a type specifier in format-string. Below is the illustration of the C library sscanf () function. Jan 27, 2012 · About the scanf () is smart enough to check, no offense since it might be just because of my poor coding skill, but there was a case I had scanf () my first int then use printf () to print it out and do the same with my second int. Right now I have it reading the data in as a char array for each character. There is no such promotion with scanf arguments, which are actually Dec 31, 2020 · You can use sscanf() to parse out each HEX value as an unsigned integer then sum them in their corrected bit order. The code works for char and char arrays. But i can get correct values if i use "int" Feb 20, 2015 · Im trying to use sscanf to read and parse a three char string into an int: char strId [4] = ““123"”; int i; int count = sscanf (strId, “”%i”" &i); I tested count==1 to see if the parse succeeds or fails and 123 succeeds correctly I want to consider this a number, aaa fails correctly I dont want to consider this a number and 2aa succeeds (count==1, i==2) but I want to identify this Aug 25, 2010 · The sscanf function can be used to convert a string containing hex digits (like 0x123) to an integer or other type. Convert String to int Using sscanf () We can use sscanf () to easily convert a string to an integer. — atooct interprets the string as octal. The example below with output should tell you what exactly each method does. The format-string controls the interpretation of the input fields, and is a multibyte character string that begins and ends in its initial shift Jul 1, 2014 · I for the life of me cant figure this out. The atoi () function accepts a string (which represents an integer) as a parameter and yields an integer value in return. May 25, 2012 · I'm sure I am missing something with regards to data types but I can't find an answer. . 3. Sep 19, 2025 · In C++, both string and int are not in the same object hierarchy, we cannot perform implicit or explicit type casting as we can do in case of double to int or float to int conversion. — atobin interprets the string as binary. Aug 10, 2016 · 1 This behavior happens because every negative integer has a corresponding unsigned value, allowing sscanf to parse negative values for an unsigned int. scanf Oct 26, 2022 · swscanf is a wide-character version of sscanf; the arguments to swscanf are wide-character strings. If Apr 3, 2023 · When I attempt to read an 8 character hexadecimal value with sscanf (), I get 0x7FFFFFFF for all values over "80000000". Nov 13, 2023 · Simple as that! ATOI stands for "ASCII to Integer". The problem is is this format I cant do much as I need both values to do a sscanf. Additionally, if you actually look up the %X conversion for sscanf (check your syntax!) you will find that the result is expected to be a unsigned int. If you want to ensure that sscanf matched a positive integer, you have to parse the string as decimal integer ("%d") and use an if statement: used. It is declared inside the <stdio. Jul 23, 2014 · I want to convert this 8 bit decimal into two 4 bit nibbles also expressed as decimals because I need to pass them to a function in that form. sscanf reads from the character string s. The sscanf() function is defined in the <stdio. Since a hexadecimal digit represents four bits, we need to shift the accumulated integer four bits to the left in order to make room for the new four-bit value. So, for example, I have the hex string "fffefffe". this is my code - unsig Jul 4, 2022 · 4-6) Same as (1-3), except that %c, %s, and %[ conversion specifiers each expect two arguments (the usual pointer and a value of type rsize_t indicating the size of the receiving array, which may be 1 when reading with a %c into a single char) and except that the following errors are detected at runtime and call the currently installed constraint handler function: any of the arguments of Aug 14, 2008 · In C, what is the most efficient way to convert a string of hex digits into a binary unsigned int or unsigned long? For example, if I have 0xFFFFFFFE, I want an int with the base10 value 4294967294. Each expects, as arguments, a control string format described below, and a set of pointer arguments indicating where the converted input should be stored. Nov 17, 2018 · Use strtok to split the character array into separate hex strings, then use long strtol( const char *restrict str, char **restrict str_end, int base ) to convert each hex string to an integral value. Either way, when I sscanf a string like "ff0000" to a unsigned long (or any value) sscanf shaves off the high Aug 28, 2011 · i am trying to scan an input file with such format r1 = 0c100009 So far I have tried this but the while loop is skipped and the output is 0. Oct 26, 2022 · The following information applies to any of the scanf family of functions, including the secure versions, such as scanf_s. I have a char[] that contains a value such as "0x1800785" but the function I want to give the value to requires an int, how can I convert this to an int? I have searched around but cannot find an a Sep 21, 2015 · I have long hex number, e. So how can I reformat this char For integer parsing, we use the $sscanf system task, which reads formatted input from a string. Count the elements that sscanf puts into the output array when it converts the string to numbers. The function takes an array like this: byte lightsoff [] = {0,1,2,0,15,2,12,9,7,10}; and I want to insert my decimal versions of the two hex nibbles into the first two array values of the above. if the hexadecimal number is stored in a string hex with the form 0x or 0X or where points are representing digits in 16 base then you can use the sscanf() function to store the value in an integer number (decimalNumber for the example below) in 10 base Specifies that the argument is a intn_t or int_leastn_t (which are the same type), for conversions taking signed integers, or uintn_t or uint_leastn_t (which are the same type), for conversions taking unsigned integers. The %d format specifier is used for decimal integers, and %h for hexadecimal. Just use a temporary variable with sscanf, and cast over to unsigned char or char, whichever is right, when you put it into the byte string. Dec 29, 2020 · 0 We use the sscanf () to convert hexadecimal value to string as follows: Well, your code is everything but a converter between hexadecimal to string. This allows it to transform string representations of numbers into actual int variables to be used in C code. It works much like scanf () but the data will be read from a string instead of the console. Then when you enter "0x12", the scanning stops at the character "x" so the value 0 is read. The LED sort of inverts the color code where 255 = darkest and 0 = brightest. The type character is the only required format field; it appears after any optional format fields. Nov 20, 2011 · If you do not want to use a loop, then you need to explicitly write out all six (or twenty) array locations (although %x is not the correct conversion character - it expects a pointer to unsigned int as its corresponding argument). h reads formatted data from a string, similar to how scanf() reads from standard input. A conversion specification causes sscanf () to read and convert characters in the input into values of a conversion specifier. g. Dec 27, 2023 · The %s %d specifiers inform sscanf () we want a string followed by integer conversion. Jul 4, 2022 · 4-6) Same as (1-3), except that %c, %s, and %[ conversion specifiers each expect two arguments (the usual pointer and a value of type rsize_t indicating the size of the receiving array, which may be 1 when reading with a %c into a single char) and except that the following errors are detected at runtime and call the currently installed constraint handler function: any of the arguments of Jun 27, 2023 · The Sscanf function allows us to scan a formatted string and extract values into variables. Alas, you can’t use sscanf () to see whether a value exists within a string. So, to read an integer from console, give the format and argument to scanf () function as shown in the following code snippet. Read formatted data from string Reads data from s and stores them according to parameter format into the locations given by the additional arguments, as if scanf was used, but reading from s instead of the standard input (stdin). It tries to match the template string to the string from which it is reading input, using conversion specifier like those of printf. This function reads the formatted input from the string buffer, so we can use the format specifiers to read the numerical characters as integers. Input a hexadecimal value using scanf () To input a value in hexadecimal format – we use "%x" or "%X" format specifier and to print the value in This would be a good answer, but you shouldn't use scanf or sscanf to read signed integers because there's a risk of signed integer overflow and that's a . u Matches an unsigned decimal integer; the next pointer must be a pointer to unsigned int. Bug 216 - scanf () conversion %i incorrectly reads unsigned hex values Summary: scanf () conversion %i incorrectly reads unsigned hex values Status: RESOLVED INVALID Alias: None Product: glibc Classification: Unclassified Component: libc (show other bugs) Version: 2. Oct 4, 2019 · scanf("%x",integer_variable); seems for me as a newbie to the scene as the only way possible to input a hex number from the keyboard (or better said the stdin file) and store it to a int variable. Apr 5, 2025 · 4. sscanf () Parameters buffer: Pointer to a null-terminated character string to read the data from. Any whitespace in the format string matches any whitespace in the input string. This format may contain conversion specifications; the results from such conversions, if any, are stored in the locations pointed to by the pointer arguments that follow format. Printing The verbs: General: %v the value in a default format when printing structs, the plus flag (%+v) adds field names %#v a Go-syntax representation of the value (floating-point infinities and NaNs print as ±Inf and NaN) %T a Go-syntax Feb 10, 2013 · I need to convert hexadecimal 4-digits values to decimal so I used ssscanf but it is not work on negative numbers For example, int test;sscanf ("0xfff6","%x",&test); return 65526 instead of -10. x Matches an unsigned hexadecimal integer (that may optionally be- gin with a prefix of 0x or 0X, which is discarded); the next Description The scanf () function reads data from the standard input stream stdin into the locations given by each entry in argument-list. A conversion specification causes fscanf (), scanf (), and sscanf () to read and convert characters in the input into values of a conversion specifier. Each task serves specific use cases, from reading single characters and lines to formatted and binary data. Explore format specifiers, practical examples, and best practices for safe string operations. h> header file. this is the code I am Mar 10, 2024 · Here, we are going to learn how to input a hexadecimal value using scanf () in C programming language? By IncludeHelp Last updated : March 10, 2024 Here, we have to declare an unsigned int variable and input a value in hexadecimal format. Otherwise, swscanf and sscanf behave identically. Am I correct is assuming that using strtoll () is not appropriate here since it returns a 64 bit signed integer? If so, is there a similar tool that will do the job? Or should I just code something from scratch? Jan 1, 2023 · A white-space character causes the fscanf, scanf, and sscanf functions to read, but not store, all consecutive white-space characters in the input up to the next character that is not a white-space character. Jul 26, 2023 · I have to handle a String coming in over UART containing a bunch of information, part of it is a MAC-address that I get by using String. Now, you want to split the hex (which is int, so 2 bytes or even 4 bytes - depends on platform), The upper part is upper part, the lower part lower part (each as 8bit bytes). int read_reg (reg_t reg) { char r, eq; Jul 1, 2019 · 本文介绍如何使用sscanf函数将字符串转换为16进制数数组（HEX数组）。示例展示了如何将字符串184263转换成0x18, 0x42, 0x63的数组形式，适用于需要进行十六进制数据处理的场景。 Jul 17, 2016 · *printf uses %0nx where n is the (nonzero) width to mean pad with zeros instead of spaces but *scanf has no such special meaning for %0nx; %08x means parse up to 8 characters in hex as an unsigned int just the same as %8x. There are 5 different ways to convert a Hex string to an Integer in C++: Create a string that contains numbers separated by whitespace characters. In this post, we will learn how to save hexadecimal values in variables in C and how to print hexadecimal values. atoi() doesn't have that overhead. Feb 28, 2018 · I use fwrite to do the modifications and scanf to get the offset and the hex instructions, however, I can't find a way to actually store them as hex. — atohex interprets the string as hexadecimal. scanf reads from the standard input stream stdin. Using sscanf to convert a string to an integer and check for errors Example 2: Using sscanf to convert a string to an integer and check for errors. Luckily, C provides built-in functionality for parsing hexadecimal numbers. Apr 1, 1999 · Hi all, Does anyone know how can I convert hexadecimal string to int or long type using MFC or other libs. fscanf reads from the named input stream. The atoi () is a library function in C that converts the numbers in string form to their integer value. h These take the form of SCNx32 and PRIx32 for lower case hex scanning / printing of 32-bit integers. base are used. Mar 19, 2012 · Note that sscanf is slow (library calls, memory usage, and overkill). The specification for scanf (and other functions) can be found in the C32 Libraries guide, not the XC32 Compiler Guide. Explanation: Jan 18, 2023 · the sscanf will convert the string to internal (hex) value. Moreover it isway too dangerous (b/c of possible buffer overrun). Jul 2, 2009 · I want to convert a hex string to a 32 bit signed integer in C++. When an address of another object is passed, the behavior is not defined by the C standard. I guess the %02X format is not the right choice here but I could not find any other way to enter hexadecimal. Learn to read user input and improve your C programming. 1) reads the data from stdin 2) reads the data from file stream stream 3) reads the data from null-terminated character string buffer Oct 12, 2017 · 2進数や8進数、10進数、16進数で表記された文字列を、整数型の数値に変換する方法を解説します。 N進文字列から整数型へ Jul 24, 2021 · #include <stdint. 5 Some key features of sscanf (): Can parse many data types like floats, strings, hex values Similar format specifiers to printf () Good for flexible parsing of mixed input Oct 23, 2025 · Using scanf is trickier than printf. Nov 5, 2025 · Package fmt implements formatted I/O with functions analogous to C's printf and scanf. For example: char *hexstr = "101E4"; In this tutorial, you will learn to use scanf () function to take input from the user, and printf () function to display output to the user with the help of examples. x Matches an unsigned hexadecimal integer (that may optionally begin with a prefix of 0x or 0X, which is Matches an unsigned hexadecimal integer (that may optionally begin with a prefix of 0x or 0X, which is discarded); the next pointer must be a pointer to unsigned int. The usual way is to accumulate the hex Oct 29, 2023 · What is the best way to use sscanf with uint8_t? When I use: Aug 5, 2010 · Is there any standard C function that converts from hexadecimal string to byte array? I do not want to write my own function. It can convert strings to integers by providing the appropriate format specifier ("%d" for integers). h> size_t convert_hex(uint8_t *dest, size_t count, const char *src) { size_t i; int value; for (i = 0; i < count && sscanf(src + i * 2, "%2x", &value) == 1; i++) { dest[i] = value; } return i; } Note however that this approach may be inefficient, with a quadratic time complexity, on architectures where the standard library computes the length of the source A format specifier for scanf follows this prototype: % [*] [width] [length]specifier Where the specifier character at the end is the most significant component, since it defines which characters are extracted, their interpretation and the type of its corresponding argument: The function sscanf () is the input analog of printf (). Not only this generates warnings: format ‘%X’ expects argument of type ‘unsigned int *’, but argument 2 has type ‘uint8_t * {aka unsigned char *}’ but it also 'erases' 4 bytes at a time in my RAM. SystemVerilog Convert string to int, hex or binary number SystemVerilog string methods allow you to convert strings to a int, hex, binary or real data type. swscanf doesn't handle Unicode full-width hexadecimal or "compatibility zone" characters. If you use the %i format specifier, it will use hex if the string starts with "0x", octal if it starts with "0" and decimal otherwise. Side question, is this stable for converting the string to an integer for use? Sep 10, 2023 · Note that some implementations of std::sscanf involve a call to std::strlen, which makes their runtime linear on the length of the entire string. it seems to only get the last 8 chars, eg - ABFFFFFFFF will become 0000FFFFFFFF. o Matches an unsigned octal integer; the next pointer must be a pointer to unsigned int. If you specifically want to match 0x___, put that into the format string: Jul 23, 2025 · This function is used for parsing the formatted strings, unlike scanf () that reads from the input stream, the sscanf () function extracts data from a string. Your code just accepts a string, and tries to output somewhat based on the conversion of the interpreted characters as hexadecimal numbers. So when you enter "012" is reads 12 since the leading 0 is essentially ignored. You probably would get better results with your own parser. The variable hex has the value as hex, 0x04D2. They always start with a % symbol and are used in the formatted string in functions like printf (), scanf, sprintf (), etc. The function’s syntax is […] In C, sscanf() is used to read formatted data. I am inputting a string from the serial port that looks like. One white-space character in format matches any combination of white-space characters in the input. %o: Reads an octal integer. It is defined in <cstdio> header file. This means that if std::sscanf is called in a loop to repeatedly parse values from the front of a string, your code might run in quadratic time (example). If we represent decimal values in hexadecimal, 10 will be A, 11 will be B etc. Jul 23, 2014 · I misunderstood what you meant about dumping String. } This parses the int, hex, string, and float values from the input using the sscanf () specifiers. Please note I am in an embedded system so every byte count. You don't need to do anything to convert it to an integer, that's what scanf does for you. C – Read Hexadecimal Number using Scanf () To read a hexadecimal number entered by user via standard input in C language, use scanf () function. So I have my MAC Address for the ethernet card in a String, and I am stuck on converting it. Alternatively (because I like and use this function a lot), sscanf . Aug 4, 2015 · x Matches an optionally signed hexadecimal integer, whose format is the same as expected for the subject sequence of the strtoul() function with the value 16 for the base argument. The below code demonstrates parsing an integer and a string from the input. Sscanf () handles reading the raw string, extracting "John" and 25 based on spacing, then storing into our variables properly. I thought sscanf took its first argument as a string, hence I can't dump String? Here's what I have so far: Dec 10, 2013 · From the scanf man page: x, X Matches an optionally signed hexadecimal integer; the next pointer must be a pointer to unsigned int. The format "%i" accepts values as 0xABCD (hex) and 1234 (decimal). Oct 27, 2014 · I want the code to run until the user enters an integer value. In this article, we will learn how to read data using sscanf () function in C. The format 'verbs' are derived from C's but are simpler. For eg:, A string like "thank you" to hex format: 7468616e6b20796f75 And from hex 7468616e6b20796f75 to string: "thank you". Apr 4, 2019 · I want to read an Hex value from a string and store it a variable, I am using sscanf but the original number is on 6 byte and I am only getting the least significant 4 bytes. Let suppose, we have two values in Hexadecimal "64" (100 in Decimal) and "FAFA" (64250 in Decimal). Syntax sscanf (source, formatted_string Mar 28, 2015 · All these are exactly the same thing once compiled: byte b = 255; byte b = 0b11111111; byte b = 0xFF; To convert a hex string to int, you can use function strtol ( or strtoul if you want a unsigned result). C++ sscanf () sscanf () prototype int sscanf( const char* buffer, const char* format, ); The sscanf() function reads the data reads the data from buffer and stores the values into the respective variables. Sep 18, 2018 · I have a variable with an hexadecimal value: in this example, a byte with value 0xfe: Multiple Inputs The scanf() function also allow multiple inputs (an integer and a character in the following example): C program to read and write hexadecimal values: Hexadecimal values are base 16 number system. Conversion specifications which are introduced by the percent sign (%) or the sequence (%n$) where n is a decimal integer in the range [1,NL_ARGMAX]. scanf () reads input from stdin (standard input), according to the given format and stores the data in the given arguments. Using sscanf this way : uint8_t buf[6]; char hex[1 We would like to show you a description here but the site won’t allow us. h> int vsscanf(const char *restrict str, const char *restrict format, va_list ap); Feb 9, 2023 · The sscanf function is called, and the string, along with hexadecimal format specifier "%X" and the integer that stores the resultant value, are passed as an argument. Reading unsuccessful Inputs: Explanation: As here the second argument entered is a string and is not matching to the format specifier '%d' that is an integer so Jul 23, 2025 · 3. I need to parse it in to a uint64_t data type. A beginner friendly guide with example and output. So, to read a hexadecimal number from console, give the format and argument to scanf () function as shown in the following Jul 23, 2025 · Output: Reading successful inputs: Explanation: Since both the input values are integers and the format specifier in the scanf () function is '%d', thus input values are read and scanf () function returns the number of values read. The value is assigned to an argument in the argument list. This is because of promotion, so that any type smaller than an int is promoted to an int when passed to printf, and float s are promoted to double. Hex (base 16) is a way of displaying a number, like binary (base 2), octal (base 8), or decimal (base 10). Using spaces is considered more elegant thought 😉 BTW, "elegant" incorporates "efficient" 😉 Dec 27, 2023 · Expert Tips for Precision Parsing Through many late nights debugging serial devices, I‘ve collected some helpful tips for squeezing maximum precision out of sscanf (): Define explicit widths for strings and integer values whenever possible. It parses a string until hitting a non-digit character, interpreting the ASCII characters as their corresponding integer values. The type character determines whether the associated argument is interpreted as a character, string, or number. It may show as a bigger source code but it gives you the chance to control and expand your code exactly as needed, without compromising security and speed. Each function reads characters, interprets them according to a format, and stores the results in its arguments. Storing hexadecimal Sep 14, 2017 · How can i convert a string to hex and vice versa in c. Each pointer argument must be of a type that is appropriate for the value returned by the corresponding conversion specification. "AA BB CC DD" or "AABBCCDD" You can use either way, your choice. Nov 8, 2022 · In C++ STL there are certain properties that help to convert a hexadecimal string or number to a decimal number easily. The above code produces following result−. %u: Reads an unsigned integer. The scanf () family of functions scans input according to format as described below. atoi () returns the integer corresponding to the ASCII decimal representation in str. This means that even a tab (\t) in the format string can match a single space character in the input string. Sep 20, 2022 · C sscanf() function: The sscanf() function is used to read data from buffer into the locations that are given by argument-list. Synopsis scan string format ? varName ? Description If string matches format, which consists of literal values, whitespace Learn how to input decimal, octal and hexadecimal values into character variables in C using scanf (). Nov 22, 2023 · The problem occurs when I need to convert the array of hexadecimal to one int value I can use. scanf("%02X", &RAM[RAM[arg]]); depending on the level of indirection. Problem How to convert the hexadecimal value to integer value by using the C programming language? Explain the concept. In the realm of handling non-numeric characters, one commonly encountered challenge is converting a string to an integer while ensuring error-free execution. Defined inside <stdlib. Nov 9, 2022 · scan , a built-in Tcl command, extracts values from a string according to the string representations indicated in a pattern specification. The key function for reading input in C is scanf() – and for hexadecimals specifically, we use the %x format specifier: int hex_val; SystemVerilog string methods allow you to convert int, hex, binary or real data type to a string. Main thing to keep in mind is: The conversion scans all leading digits and underscore characters ( _ ) and stops as soon as it encounters any other character or the end of the string. For example use %6d rather than just %d to catch overflow issues early. Both suffer from the problem that out-of-range values result in undefined behavior. Dec 31, 2014 · I need to scan a hex representation of 6 bytes data and store it in a 6 byte array. See Also Dump a file in hex and ASCII Binary scan Like scan but matches binary representations rather than textual representations. The fwrite actually writes 4D FF 33 FD FE as text inside the binary file instead of hex. Apparently the newer versions of the IDE have shut down many of the ways to accomplish this and after hours I am stuck. Nov 8, 2022 · sscanf with %x should be used only with the address of an unsigned int. t0x123,FF,00,01,01,D6,00,FF,F1 I need to take that data and make it into an array of int values. Is there any library function available which will convert a passed hex string to its equivalent integer value??? Something like atoi () except that the input contains a hexadecimal string ("1A2" => 418). sscanf () reads from the string string and interprets it according to the specified format. a3dafc126e (10 characters long) which I want to read and convert to decimal number using sscanf: Apr 4, 2014 · 23 196 /*hexadecimal*/ 56 /*octal*/ The only issue that I can see is the parsing to find the difference between a decimal integer and an octal. While the atoi function in C/C++ can be used for this purpose, it has certain Oct 13, 2025 · In C, atoi stands for ASCII To Integer. sscanf doesn't handle multibyte hexadecimal characters. Dec 8, 2019 · After hours of searching and trials. The sscanf() function in C stdio. String to int Conversion Using stoi () Function The stoi () function in C++ takes a string as an argument and returns its value in integer form. So I have a hex string that represents a 64 bit unsigned integer. Every time I use a string-to-int function, like atoi (), it will always return 0. Numbers from 0 to 9 and characters from A to F are used to represent a hexadecimal value. As with scanf (), the sscanf () function stops reading when a whitespace character is encountered. 2 I mportance: P2 normal Target Milestone: --- Assignee: GOTO Masanori URL Sep 21, 2020 · The %d format specifier to scanf explicitly expects a number formatted as a decimal integer. h&gt; int main() { int n; printf(&quot; In the C Programming Language, the sscanf function reads a formatted string from the stdin stream. Nov 5, 2023 · Reading Hexadecimal Values in C Code A core task when dealing with hex is reading an inputted hexadecimal value as part of a C program. It's as if sscanf () is confusing signed and unsigned numbers. The sscanf() function reads data from a char array and writes it into memory locations specified by the arguments. I assume I save them wrong in the char in the first place. Assigning the Hexadecimal number in a variable There is no special type of data type to store Hexadecimal values in C programming, Hexadecimal number is an integer value and you can store it in the integral type of data types (char, short or int). The binary representation of this is Jun 1, 2015 · I have a issue trying to use scanf to get a big hexadecimal num (12 chars) from the user. Nov 1, 2025 · The format specifier in C is used to tell the compiler about the type of data to be printed or scanned in input and output operations. However, unlike scanf(), sscanf() does not read from standard input—it reads from a character string. The sscanf function accepts a string from which to read input, then, in a manner similar to printf and related functions, it accepts a template string and a series of related arguments. You would use Hi, I am trying to convert the string from ctime to a struct but i always get garbage values if i use "uint8_t". Is there a different way to input a hex value from the stdin and store it into an integer variable? Bonus challenge: It would be nice also, if i could write negative values (through negative hex Mar 9, 2012 · scanf data in hex format into unsigned shorts Asked 13 years, 8 months ago Modified 5 years, 2 months ago Viewed 9k times This beginner-friendly guide explains how to use scanf () to read hex values, with a working example and clear steps. Running this would print: int: 128 hex: 0xff str: hello float: 42.