Read a file by bytes in BASH

Question

I need to read first byte of file I specified, then second byte,third and so on. How could I do it on BASH? P.S I need to get HEX of this bytes

Answer 1

using read a single char can be read at a time as follows:

read -n 1 c
echo $c   

[ANSWER]

Try this:

#!/bin/bash
# data file
INPUT=/path/to/input.txt

# while loop
while IFS= read -r -n1 char
do
        # display one character at a time
    echo  "$char"
done < "$INPUT"

From this link

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Second method, Using awk, loop through char by char

awk '{for(i=1;i<=length;i++) print substr($0, i, 1)}' /home/cscape/Desktop/table2.sql

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third way,

$ fold -1 /home/cscape/Desktop/table.sql  | awk '{print $0}'

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EDIT: To print each char as HEX number:

Suppose I have a file name file :

$ cat file
123A3445F 

I have written a awk script (named x.awk) to that read char by char from file and print into HEX :

$ cat x.awk
#!/bin/awk -f

BEGIN    { _ord_init() }

function _ord_init(    low, high, i, t)
{
    low = sprintf("%c", 7) # BEL is ascii 7
    if (low == "\a") {    # regular ascii
        low = 0
        high = 127
    } else if (sprintf("%c", 128 + 7) == "\a") {
        # ascii, mark parity
        low = 128
        high = 255
    } else {        # ebcdic(!)
        low = 0
        high = 255
    }

    for (i = low; i <= high; i++) {
        t = sprintf("%c", i)
        _ord_[t] = i
    }
}
function ord(str,    c)
{
    # only first character is of interest
    c = substr(str, 1, 1)
    return _ord_[c]
}

function chr(c)
{
    # force c to be numeric by adding 0
    return sprintf("%c", c + 0)
}

{ x=$0; printf("%s , %x\n",$0, ord(x) )} 

To write this script I used awk-documentation
Now, You can use this awk script for your work as follows:

$ fold -1 /home/cscape/Desktop/file  | awk -f x.awk
1 , 31
2 , 32
3 , 33
A , 41
3 , 33
4 , 34
4 , 34
5 , 35
F , 46

NOTE: A value is 41 in HEX decimal. To print in decimal change %x to %d in last line of script x.awk.

Give it a Try!!