Improve remove_leading_whitespace.sh: add error handling, file checks…

src/remove_leading_whitespace.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+# remove_leading_whitespace.sh
+# Removes leading whitespace (spaces or tabs) from each line.
+# Usage:
+#   ./remove_leading_whitespace.sh filename   # Cleans file in place
+#   cat file | ./remove_leading_whitespace.sh # Cleans piped input, outputs to stdout
+
+set -euo pipefail
+
+if [ "$#" -eq 1 ]; then
+    # File mode: clean file in place
+    file="$1"
+    if [ ! -f "$file" ]; then
+        echo "Error: File '$file' does not exist." >&2
+        exit 2
+    fi
+    if [ ! -w "$file" ]; then
+        echo "Error: File '$file' is not writable." >&2
+        exit 3
+    fi
+    tmpfile=$(mktemp --tmpdir "rlw.XXXXXX")
+    trap 'rm -f "$tmpfile"' EXIT
+    if sed 's/^[ \t]*//' "$file" > "$tmpfile"; then
+        mv -- "$tmpfile" "$file"
+        trap - EXIT
+    else
+        echo "Error: Failed to process file." >&2
+        exit 4
+    fi
+elif [ "$#" -eq 0 ]; then
+    # Pipe mode: clean stdin, output to stdout
+    sed 's/^[ \t]*//'
+else
+    echo "Usage: $0 [filename]" >&2
+    exit 1
+fi