Linux string to number one

Taufan Lubis – Ubuntu Linux

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Linux Programming with Assembly Language – Convert ASCII string to Number

November 25, 2018 by taufanlubis

In assembly, register only know ASCII (American Standard Code for Information Interchange) characters. It mean, If you are working with number and need to display the result by calling syscall number 4 (32 bit x86), you can’t just put the result address into ecx register. Because, the ecx register will assume that your result in Hex number.
For example, your result is 7. ecx will assume that it’s 7hexadesimal not 7decimal meanwhile 7 is 37hexadesimal in ASCII table.

Let’s try in coding to see how it works.
It’s very simple program. I just do simple math, 4+2=6. I add 4 into eax register and 2 into ebx register. Then add ebx register to eax register, so the result will be:
eax = eax + ebx.
= 4 + 2
= 6

But why, the result is not ‘6′ as I expected.
Let’s use gnu debugger to explore the code. You have to re-compile again with option -gstabs for enable the debugger function.

List down the codes so we can set where is the break start.

Set break on line 5.

Set, assembly format to Intel instead of the default, AT&T.

Run the program

Check the current instruction.

Check register eax, ebx and ecx. It’s still empty

Go to next instruction and check the register again.

Check current instruction position.

Go to next instruction and check the register.

Check position of current instruction.

Go to next intruction and check the registers. Ebx register already added into eax register.

Content of eax is moved to memory then from memory is moved to ecx register.

Now, let’s see the content of ecx register.

It’s not ‘6‘ is ‘\006‘, that’s why the result is wrong.
Why it happens? Because ecx register will assume that it is a character not value.
If you check in ASCII table, 6 hex is ACK (acknowledge) which is can not be displayed.

So, how we convert ascii into number?

If you see ASCII table below:
character → hex number
0 → 30
1 → 31
2 → 32
3 → 33
4 → 34
5 → 35
6 → 36
7 → 37
8 → 38
9 → 39

If I want to convert character ‘6‘ into number ‘6‘, I just need to add ‘30‘, so it will become 36 in hexadecimal number or ‘6‘ in character.
So, if we go back to our code, we just add ‘30‘ before we send to ecx character to ‘result’ memory variable.

Well, it works now.
Check again with use gnu debugger again to see how it work.

Just set break to 9.

Run the program and disassemble it.

Check the registers.

Go to next intruction and check the registers. Eax register now has 0x36 or 36hexadecimal or ‘6‘ in character. What is ‘54‘, it’s decimal of 36 hexadecimal. We are talking about character now not value.

Go to next instruction few times until instruction pointer is at 0x080480a3.

Check the string character in ecx register. It’s ‘6‘. So it’s correct.

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Thread: Shell script: convert string to number

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Shell script: convert string to number

I’m very new to shell scripting in Bash.

I’m trying to figure out how to treat the output of stat -c %s filename as a number, and not as a string. If you run that command, it will output the size of the file in bytes.

Here’s the script I’m working on. It iterates over every file in the working directory, and attempts to print the cumulative size of all the files over which it iterated so far.

The problem should be evident from the output:

/Pictures$ ./print-cumulative-sizes.sh
1036228+0
970325+1036228+0
1108950+970325+1036228+0
1476318+1108950+970325+1036228+0
1027836+1476318+1108950+970325+1036228+0
1050479+1027836+1476318+1108950+970325+1036228+0
1156703+1050479+1027836+1476318+1108950+970325+103 6228+0
1215533+1156703+1050479+1027836+1476318+1108950+97 0325+1036228+0
960132+1215533+1156703+1050479+1027836+1476318+110 8950+970325+1036228+0
1569659+960132+1215533+1156703+1050479+1027836+147 6318+1108950+970325+1036228+0
1149074+1569659+960132+1215533+1156703+1050479+102 7836+1476318+1108950+970325+1036228+0
4096+1149074+1569659+960132+1215533+1156703+105047 9+1027836+1476318+1108950+970325+1036228+0
98528+4096+1149074+1569659+960132+1215533+1156703+ 1050479+1027836+1476318+1108950+970325+1036228+0
142+98528+4096+1149074+1569659+960132+1215533+1156 703+1050479+1027836+1476318+1108950+970325+1036228 +0
142+142+98528+4096+1149074+1569659+960132+1215533+ 1156703+1050479+1027836+1476318+1108950+970325+103 6228+0

See what’s wrong? How can I get bash to treat my $SIZE and $TOTAL variables as numbers, not as strings?

Thank you in advance for any help!

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strtol(3) — Linux man page

strtol, strtoll, strtoq — convert a string to a long integer

Synopsis

Description

The strtol() function converts the initial part of the string in nptr to a long integer value according to the given base, which must be between 2 and 36 inclusive, or be the special value 0.

The string may begin with an arbitrary amount of white space (as determined by isspace(3)) followed by a single optional ‘+’ or ‘-‘ sign. If base is zero or 16, the string may then include a «0x» prefix, and the number will be read in base 16; otherwise, a zero base is taken as 10 (decimal) unless the next character is ‘0’, in which case it is taken as 8 (octal).

The remainder of the string is converted to a long int value in the obvious manner, stopping at the first character which is not a valid digit in the given base. (In bases above 10, the letter ‘A’ in either upper or lower case represents 10, ‘B’ represents 11, and so forth, with ‘Z’ representing 35.)

If endptr is not NULL, strtol() stores the address of the first invalid character in *endptr. If there were no digits at all, strtol() stores the original value of nptr in *endptr (and returns 0). In particular, if *nptr is not ‘\0’ but **endptr is ‘\0’ on return, the entire string is valid.

The strtoll() function works just like the strtol() function but returns a long long integer value.

Return Value

The strtol() function returns the result of the conversion, unless the value would underflow or overflow. If an underflow occurs, strtol() returns LONG_MIN. If an overflow occurs, strtol() returns LONG_MAX. In both cases, errno is set to ERANGE. Precisely the same holds for strtoll() (with LLONG_MIN and LLONG_MAX instead of LONG_MIN and LONG_MAX).

Errors

(not in C99) The given base contains an unsupported value.

The resulting value was out of range. The implementation may also set errno to EINVAL in case no conversion was performed (no digits seen, and 0 returned).

Conforming To

strtol() conforms to SVr4, 4.3BSD, C89, C99 and POSIX.1-2001, and strtoll() to C99 and POSIX.1-2001.

Notes

Since strtol() can legitimately return 0, LONG_MAX, or LONG_MIN (LLONG_MAX or LLONG_MIN for strtoll()) on both success and failure, the calling program should set errno to 0 before the call, and then determine if an error occurred by checking whether errno has a nonzero value after the call.

According to POSIX.1-2001, in locales other than the «C» and «POSIX», these functions may accept other, implementation-defined numeric strings.

BSD also has with completely analogous definition. Depending on the wordsize of the current architecture, this may be equivalent to strtoll() or to strtol().

Example

The program shown below demonstrates the use of strtol(). The first command-line argument specifies a string from which strtol() should parse a number. The second (optional) argument specifies the base to be used for the conversion. (This argument is converted to numeric form using atoi(3), a function that performs no error checking and has a simpler interface than strtol().) Some examples of the results produced by this program are the following:

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Linux string to number one

Sep 06, 2021 · Converting string variables to numbers. Let’s declare some «numbers» which are basically strings of characters. [email protected]:

$ b=3. You can check the assigned number: [email protected]:

$ echo $a 11 [email protected]:

[SOLVED] Converting string to number in bash

Oct 07, 2012 · Converting string to integer in BASH: pgb205: Programming: 17: 08-31-2010 08:38 PM: converting string in integer in bash script: dziadgba: Linux — Newbie: 5: 08-31-2009 05:59 PM [Bash] increment number in a string: czezz: Programming: 4: 07-01-2009 11:34 AM: Getting a number out of a string in bash: Luc484: Programming: 5: 01-20-2006 02:15 AM: converting string to asterisks: pantera

Convert a String to a Number — UNIX

Mar 17, 2017 · echo «Number = $number» # Number = 3. number=three. echo «Number = $number» # Number = 0. # Tries to evaluate the string «three» as an integer. Certain arithmetic operations are permitted for declared integer variables without the need for expr or let. n=6/3. echo «n = $n» # n = 6/3. declare -i n. n=6/3.

Argument string to integer in bash — Unix & Linux Stack .

Sep 27, 2015 · To perform arithmetic, you should invoke the arithmetic expansion operator $ ( (. )). For example: $ a=2 $ echo «$a + 1» 2 + 1 $ echo «$ ( ($a + 1))» 3. or generally preferred: $ echo «$ ( (a + 1))» 3. You should be aware that bash (as opposed to ksh93, zsh or yash) only performs integer arithmetic.

C String to Int: Simple Ways to Convert to Numeric Values .

May 27, 2014 · #include int main() < unsigned char text[]="1234"; int integerValue; sscanf(text, "%d", &integerValue); printf("Integer value is: %d", integerValue); return0; > Example 4: A program to convert a string to an integer using the strtol() function. The C strlol() function converts a string to a long integer. This is a 64-bit integer.

AWK: convert string to numeric, how? | Howtoforge — Linux .

Jun 09, 2008 · isLoad15=$ (uptime | awk ‘ < print $NF >‘) maxLoad15=2.00 if [ «$isLoad15» gt «$maxLoad15» ] then …. into a numeric, as required for the «gt — condition». this would mean I’d have to do it all in AWK, but I’d need the var in the shell script, as there are several existing scripts which only need the «isLoad15» value.

How to convert String to Numeric in sql

How to convert String to Numeric. To convert a String to Numeric uses sql conversion functions like cast or convert. Syntax. CAST ( expression AS datatype [ ( length ) ] ) CONVERT ( datatype [ ( length ) ] , expression [ , style ] ) Examples. SELECT CAST(‘127’ AS NUMERIC); SELECT CAST(‘127.86’ AS …

Java Syntax: Converting Strings to Numbers

Jul 03, 2019 · Converting Numbers to Strings. To make a number into a String follows the same sort of pattern as the String class has a valueOf method too. It can take any of the primitive data type numbers as an argument and produce a String: int numberTwenty = 20; String converted = String…

converting string to number in shell script — UNIX

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How to Convert String to Number in JavaScript

The first argument of parseInt must be a string. parseInt will return an integer found in the beginning of the string. Remember, that only the first number in the string will be returned. For example when we have the string “384.75a” and we want to convert it to a number, the result will be 384.

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The syntax for the TO_NUMBER function in Oracle/PLSQL is: TO_NUMBER( string1 [, format_mask] [, nls_language] ) Parameters or Arguments string1 The string that will be converted to a number. format_mask Optional. This is the format that will be used to convert string1 to a number…

strsignal(3): return string describing signal — Linux man page

• Synopsis
• Description
• Return Value

• strsignal():
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Bash split string into array using 4 simple methods .

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strings(1) — Linux manual page

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linux — How to test if a variable is a number in Bash — By .

This rejects empty strings and strings containing non-digits, accepting everything else. Negative or floating-point numbers need some additional work. . How to test if a variable is a number in Bash linux red hat debian opensuse ubuntu arch linux mandrake get link linux computer linux pc linux server linux desktop learn linux red hat linux .

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