NDISASM(1) The Netwide Assembler Project NDISASM(1)

# [NAME](#NAME)

ndisasm - the Netwide Disassembler, an 80x86 binary file disassembler

# [SYNOPSIS](#SYNOPSIS)

**ndisasm** \[ **-o** origin ] \[ **-s** sync-point \[...]] \[ **-a** | **-i** ] \[ **-b** bits ] \[ **-u** ] \[ **-e** hdrlen ] \[ **-p** vendor ] \[ **-k** offset,length \[...]] infile

# [DESCRIPTION](#DESCRIPTION)

The **ndisasm** command generates a disassembly listing of the binary file infile and directs it to stdout.

# [OPTIONS](#OPTIONS)

**-h**

Causes **ndisasm** to exit immediately, after giving a summary of its invocation options.

**-r**|**-v**

Causes **ndisasm** to exit immediately, after displaying its version number.

**-o** *origin*

Specifies the notional load address for the file. This option causes **ndisasm** to get the addresses it lists down the left hand margin, and the target addresses of PC-relative jumps and calls, right.

**-s** *sync-point*

Manually specifies a synchronisation address, such that **ndisasm** will not output any machine instruction which encompasses bytes on both sides of the address. Hence the instruction which starts at that address will be correctly disassembled.

**-e** *hdrlen*

Specifies a number of bytes to discard from the beginning of the file before starting disassembly. This does not count towards the calculation of the disassembly offset: the first *disassembled* instruction will be shown starting at the given load address.

**-k** *offset,length*

Specifies that *length* bytes, starting from disassembly offset *offset*, should be skipped over without generating any output. The skipped bytes still count towards the calculation of the disassembly offset.

**-a**|**-i**

Enables automatic (or intelligent) sync mode, in which **ndisasm** will attempt to guess where synchronisation should be performed, by means of examining the target addresses of the relative jumps and calls it disassembles.

**-b** *bits*

Specifies 16-, 32- or 64-bit mode. The default is 16-bit mode.

**-u**

Specifies 32-bit mode, more compactly than using ‘-b 32’.

**-p** *vendor*

Prefers instructions as defined by *vendor* in case of a conflict. Known *vendor* names include **intel**, **amd**, **cyrix**, and **idt**. The default is **intel**.

# [RESTRICTIONS](#RESTRICTIONS)

**ndisasm** only disassembles binary files: it has no understanding of the header information present in object or executable files. If you want to disassemble an object file, you should probably be using [**objdump**(1)](/man/os/nasm/objdump.1).

Auto-sync mode won’t necessarily cure all your synchronisation problems: a sync marker can only be placed automatically if a jump or call instruction is found to refer to it *before* **ndisasm** actually disassembles that part of the code. Also, if spurious jumps or calls result from disassembling non-machine-code data, sync markers may get placed in strange places. Feel free to turn auto-sync off and go back to doing it manually if necessary.

# [SEE ALSO](#SEE_ALSO)

[**objdump**(1)](/man/os/nasm/objdump.1)

10/25/2026 NASM

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Document: ndisasm(1) from nasm 3.02-r2 (Chainguard OS)
Source: https://github.com/netwide-assembler/nasm