exhash 0.3.1

Verified line-addressed file editor using lnhash addresses

exhash — Verified Line-Addressed File Editor

exhash combines Can Bölük's very clever line number + hash editing system with the powerful and expressive syntax of the classic ex editor.

Install via pip to get both a convenient Python API, and native CLI binaries:

pip install exhash

Or install just the CLI binaries via cargo:

cargo install exhash

lnhash format

We refer to an lnhash as a tag of the form lineno|hash|, where hash is the lower 16 bits of Rust's DefaultHasher over the line content.

Address forms:

• lineno|hash| — hash-verified address
• $ — last line (no hash)
• % — whole file (1,$, no hashes)

CLI

The native Rust binaries are installed into your PATH via pip.

View

# Shows every line prefixed with its lnhash
lnhashview path/to/file.txt
# Optional line number range to show
lnhashview path/to/file.txt 10 20

Edit

# Substitute on one line
exhash file.txt '12|abcd|s/foo/bar/g'

# Transliterate characters on one line
exhash file.txt '12|abcd|y/abc/ABC/'

# Append multiline text (terminated by a single dot)
exhash file.txt '12|abcd|a' <<'EOF'
new line 1
new line 2
.
EOF

# Dry-run
exhash --dry-run file.txt '12|abcd|d'

# Set shift width for < and >
exhash --sw 2 file.txt '12|abcd|>1'

# Last line and whole file shorthands (no hash)
exhash file.txt '$d'
exhash file.txt '%j'

# Move a line to EOF using $ as the destination
exhash file.txt '12|abcd|m$'

Substitute uses Rust regex syntax:

• Pattern syntax is from regex
• Replacement syntax is from regex::Replacer, e.g. $1, $0, ${name}
• \/ escapes the command delimiter in pattern/replacement
• Custom delimiters: s, y, g, g!, and v all accept any non-alphanumeric char as delimiter instead of /, e.g. s@pat@rep@, g@pat@cmd. Each command in a combo picks its own delimiter independently: g@a/b@s/old/new/
• Literal newlines in pattern/replacement are supported (joins/splits lines as needed)
• Transliteration uses y/src/dst/ and requires source/destination to have equal character counts

When passing multiple commands, each command's lnhashes are verified immediately before that command runs.

For a/i/c commands, provide the text block on stdin:

printf "new line 1\nnew line 2\n.\n" | exhash file.txt "2|beef|a"

Stdin filter mode

cat file.txt | exhash --stdin - '1|abcd|s/foo/bar/'

In --stdin mode, multiline a/i/c text blocks are not available.

Python API

from exhash import exhash, exhash_file, lnhash, lnhashview, lnhashview_file, line_hash

Viewing

text = "foo\nbar\n"
view = lnhashview(text)       # ["1|a1b2|  foo", "2|c3d4|  bar"]
view = lnhashview_file("f.py") # same but reads from file

Editing

exhash(text, cmds, sw=4) takes the text and a required iterable of command strings (use [] for no-op). sw controls how far < and > shift. For a/i/c commands, lines after the command are the text block. Do not include an ex-style trailing . line here: unlike CLI/script mode, exhash(text, cmds) does not use one, and a final . line is inserted literally.

addr = lnhash(1, "foo")  # "1|a1b2|"
res = exhash(text, [f"{addr}s/foo/baz/"])
print(res["lines"])    # ["baz", "bar"]
print(res["modified"]) # [1]

# Multiple commands
a1, a2 = lnhash(1, "foo"), lnhash(2, "bar")
res = exhash(text, [f"{a1}s/foo/FOO/", f"{a2}s/bar/BAR/"])

# Hashes are checked just-in-time per command.
# If earlier commands change/shift a later target line, recompute lnhash first.

# Append multiline text (no dot terminator)
res = exhash(text, [f"{addr}a\nnew line 1\nnew line 2"])

# Wrong for the Python API: the trailing "." would be inserted literally
# res = exhash(text, [f"{addr}a\nnew line 1\nnew line 2\n."])

# Change shift width for < and >
res = exhash(text, [f"{addr}>1"], sw=2)

# Custom delimiters (useful when pattern/replacement contains /)
res = exhash(text, [f"{addr}s|foo|bar|"])

# Literal newlines in pattern/replacement (joins/splits lines)
a1, a2 = lnhash(1, "foo"), lnhash(2, "bar")
res = exhash("foo\nbar\n", [f"{a1},{a2}s/foo\nbar/replaced/"])

File helpers

exhash_file and lnhashview_file read directly from a file path:

view = lnhashview_file("file.py")

# Returns EditResult, file unchanged
res = exhash_file("file.py", [f"{addr}s/foo/bar/"])

# With inplace=True, writes back on success and returns diff string
diff = exhash_file("file.py", [f"{addr}s/foo/bar/"], inplace=True)

EditResult

exhash() returns an EditResult with attributes (also accessible via res["key"]):

• lines — list of output lines
• hashes — lnhash for each output line
• modified — 1-based line numbers of modified/added lines
• deleted — 1-based line numbers of removed lines (in original)
• origins — for each output line, the 1-based original line number (None if inserted)

res.format_diff(context=1) returns a unified-diff-style summary showing only changed lines with context:

res = exhash(text, [f"{addr}s/foo/baz/"])
print(res.format_diff())
# -1|a1b2|  foo
# +1|c3d4|  baz
#  2|e5f6|  bar

Tests

cargo test && pytest -q