elidelong: command-line filter to elide long lines

README.md

@@ -15,6 +15,7 @@ This repository hosts various small personal tools.
 - [`csv2json`](csv2json): transform CSV into JSON
 - [`csv2table`](csv2table): pretty-print a CSV file with ASCII-art table
 - [`dpkg-imediff`](dpkg-imediff): when dpkg interactively prompts for resolving a config file conflict, run this to start a merge editor
+- [`elidelong`](elidelong): command-line filter to elide long lines
 - [`exiforientergui`](exiforientergui): GUI to losslessly modify EXIF orientation of an image
 - [`ffmcut`](ffmcut): ffmpeg wrapper to cut a video between 2 timestamps
 - [`firefox-relay-tools/fxrelay-add`](firefox-relay-tools/fxrelay-add): add a Firefox Relay address

elidelong/elidelong

@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+
+# SPDX-License-Identifier: WTFPL
+
+import argparse
+import os
+import signal
+import sys
+#import fileinput
+
+
+def has_colors():
+    if os.environ.get("NO_COLOR"):
+        return False
+    if os.environ.get("CLICOLOR_FORCE") or os.environ.get("FORCE_COLOR"):
+        return True
+    return sys.stdout.isatty()
+
+
+def main():
+    signal.signal(signal.SIGINT, signal.SIG_DFL)
+    signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument("-l", "--length", type=int, default=80)
+    parser.add_argument("file", default="-", nargs="?")
+    args = parser.parse_args()
+
+    if args.file == "-":
+        fp = sys.stdin
+    else:
+        fp = open(args.file)
+
+    with fp:
+        skip_until_nl = False
+        buf = ""
+        while True:
+            if not buf:
+                buf = fp.readline(args.length)
+                if not buf:
+                    break
+
+            elif len(buf) < args.length:
+                buf += fp.readline(args.length - len(buf))
+
+            pos = buf.find("\n")
+            if pos >= 0:
+                if skip_until_nl:
+                    buf = buf[pos + 1:]
+                else:
+                    line, buf = buf[:pos], buf[pos + 1:]
+                    print(line)
+                skip_until_nl = False
+
+            else:
+                if skip_until_nl:
+                    buf = ""
+                else:
+                    print(buf)
+                    skip_until_nl = True
+
+
+if __name__ == "__main__":
+    main()

elidelong/test.sh

@@ -0,0 +1,43 @@
+#!/bin/sh -eu
+# SPDX-License-Identifier: WTFPL
+# shellcheck enable=
+
+cd "$(dirname "$0")"
+
+got=$(mktemp sorted.XXXXXX)
+trap 'rm "$got"' EXIT
+
+
+init () {
+	./elidelong "$@" > "$got"
+}
+
+check () {
+	diff -u - "$got"
+}
+
+
+# basic test
+init -l 4 <<- EOF
+	a
+	bc
+	def
+	ghij
+	klmno
+	pqrstu
+	vwxyz
+
+	012345
+EOF
+
+check <<- EOF
+	a
+	bc
+	def
+	ghij
+	klmn
+	pqrs
+	vwxy
+
+	0123
+EOF