Hex edit on linux

There are several useful tools which can be used to view and edit a binary file in hex mode.
(1) xxd (make a hexdump or do the reverse)
xxd infile        //hex dump. By default, in every line 16 bytes are displayed.
xxd -b infile    //bitdump instead of hexdump
xxd -c 10 infile //in every line 10 bytes are displayed instead of default value 16.
xxd -g 4 infile  //every 4 bytes form a group and groups are separated by whitespace.
xxd -l 100 infile     //just output 100 bytes
xxd -u infile    //use upper case hex letters.
xxd -p infile    //hexdump is displayed in plain format, no line numbers.
xxd -i infile     // output in C include file style.
E.g. output looks like:
unsigned char __1[] = {
  0x74, 0x65, 0x73, 0x74, 0x0a
};
unsigned int __1_len = 5;

xxd -r -p infile //convert from hexdump into binary. This requires a plain hex dump format(without line numbers).
E.g. in the infile, content should look like: 746573740a.
Note: additional whitespace and new-breaks are allowed. So 74 65 73 740a is also legal.
xxd -r infile     //similar to last command except line numbers should be specified also.
E.g. in the infile, content should look like: 0000000: 7465 7374 0a.

xxd can easily be used in vim which is described here.

(2) od(dump files in octal and other formats)
Switches:
    -A  how offsets are printed
    -t  specify output format
        (d:decimal; u:unsigned decimal;o:octet; x: hex; a: characters; c:ASCII characters or escape sequences.
        Adding a z suffix  to any type adds a display of printable characters to the end of each line of output)
    -v  Output consecutive lines that are identical.
    -j   skip specified number of bytes first.
    -N  only output specified number of bytes.

Example:
dd bs=512 count=1 if=/dev/hda1 | od -Ax -tx1z -v

(3) hexdump/hd
Currently, I have not used this command. Maybe in the near future I will update this part if I get experience about hexdump.