Редактор

Эта страница — документ из репозитория, и она на английском.

The editor (F4)

Lines, with a block, undo over the whole session, and a save that writes a new file beside the old one and renames it over the top — so an interrupted save never leaves half a file.

F2 saves, Shift+F2 saves under another name, F7 opens the same search dialog the viewer has — text, hex or a regular expression, case, whole words, forwards or backwards — and Ctrl+F7 replaces. Ctrl+Z and Ctrl+Y undo and redo. F6 hands the file to the viewer at the same line.

A column block is a rectangle rather than a run of lines, which is how a column of numbers is moved without touching what is beside it.

Colours

A file whose name says what it is — Rust, C, C++, Java, C#, JavaScript, TypeScript, PHP, Python, Ruby, Go, shell, SQL, HTML, XML, CSS, Markdown, JSON, TOML, YAML, INI, Make, Dockerfile, Lua, Perl — is coloured as you read it, and the status line names the language so you can see at once when a file is being read as something you did not mean. The colours come from the theme, so they follow it. ui.syntax = false in fcmd.toml turns them off.

Bytes instead of lines

F4 on a binary opens the same editor on its bytes, and Alt+H switches either way. Two panes, the hex and the text; Tab moves between them and both type. Insert chooses between overwriting and inserting — in a binary a shifted byte usually breaks the file, so overwriting is what it starts in.

Changed bytes are drawn as changed until they are written, with the list of what changed beside them: offset, old byte, new byte. Ctrl+Z takes one back. F2 writes, atomically.

F3 marks a block and F12 says what to do with it: write it out to a file, read a file in, fill it with a byte, exclusive-or it with a key, copy or move bytes from elsewhere in the same file, insert zeros, delete. Each one says what the file's length will become before it happens.

F9 assembles one instruction where the cursor is — ret, xor eax, eax, mov rax, 1, jmp 0x401010, call rax. A branch is written as the address you want to arrive at, not as a displacement. Whatever it encodes is decoded again before it is shown, so what you see is the instruction the processor will see.

Addresses are written the way a disassembly prints them: mov eax, [rbx], [rbx+8], [rbx+rcx*4+8], [0x401000], and [rip+0x2e35] with the displacement counted from the end of the instruction, so a line read off the screen can be typed straight back. When no register says how wide the thing at the address is, a size word does: mov dword [rbx], 1, or byte ptr if you write masm. Without one it asks rather than guess, because one byte and eight are not the same patch. What it will not do — segment prefixes, far pointers, the floating-point and vector registers — it refuses by name.

Alt+= is the calculator: one line of arithmetic answered in decimal, hex, octal, binary and as characters at once. It reads the literals binary tools print — 0x1f, 1Fh, 0b1010, 'PE' — and the same reader takes the numbers typed into the assembler and the block operations.

Devices

On Linux and macOS a disk is a file, so the hex editor opens /dev/sdb read-only and the status line says what it is and how long it measured. The bytes are written out to a file, never back over the disk.

On Windows the same works with the names Windows uses: \\.\PhysicalDrive0 for a disk and \\.\C: for a volume, typed in rather than found in a panel — the filesystem does not list them. The length comes from the device itself, since there is nothing to measure by seeking, and the reading is done in whole sectors because that is all such a handle accepts. It needs Administrator rights, and says so if it does not have them.

Tabs, whitespace and the odd key

F9 → Options → Editor settings has the six that matter. Tabs is three choices and not a box: leave them as they are, turn a newly typed tab into spaces, or expand every tab in the file when it is opened — the last one changes the file, so it says how many lines it touched and the next save writes that. Show spaces and tabs draws a space as · and a tab as → and its padding, which is how a mixed indent becomes visible. The cursor lands after the text a search found is for typing over what was found rather than reading it.

The cursor may go past the end of a line is off by default. On, the arrows go into the columns to the right of the text instead of jumping to the next line, which is what you want to line up a column of numbers or to mark the same columns down lines of different lengths. Moving about there writes nothing: the spaces appear at the keystroke that puts a character in one of those columns, as part of the same edit, so one Ctrl+Z takes the character and its padding away together. Backspace and Del out there move the cursor and leave the file alone.

Ctrl+Q puts the next key in as itself: a control character, or a real tab where tabs are being expanded. There is no other way to get either into a file.

Alt+I and Alt+U move the block — or, with nothing selected, the line the cursor is on — one indent right and left. Tab still types a tab, because that is the key one presses while writing.

Ctrl+Shift+Ins adds the block to what is already on the clipboard instead of replacing it, so a few pieces can be gathered from here and there and pasted in one go. Ctrl+N and Ctrl+E put the cursor on the first and the last line on the screen, leaving the screen where it is.