diff_preview
Preview file changes before applying them by showing a diff of modifications that would be made by sed, awk, or perl commands.
Instructions
Preview what changes would be made by showing a diff
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| file | Yes | File to preview changes for | |
| command | Yes | Command that would make changes (e.g., "s/old/new/g") | |
| tool | No | Which tool to use for the preview | perl |
Implementation Reference
- src/index.ts:760-799 (handler)The main handler function for the 'diff_preview' tool. It creates a temporary copy of the file, applies the specified command using the chosen tool (perl, sed, or awk), generates a unified diff between original and modified temp file, returns the diff preview, and cleans up the temp file.case 'diff_preview': { const { file, command, tool = 'perl' } = args; if (!existsSync(file)) { throw new Error(`File not found: ${file}`); } // Create temp file const tempFile = `${file}.preview.tmp`; await execAsync(`rm -f .bak; cp '${file}' '${tempFile}'`); // Apply command to temp file let editCmd; switch (tool) { case 'perl': editCmd = `perl -i -pe '${command}' '${tempFile}'`; break; case 'sed': editCmd = `sed -i.tmp '${command}' '${tempFile}' && rm -f '${tempFile}.tmp'`; break; case 'awk': editCmd = `awk '${command}' '${tempFile}' > '${tempFile}.new' && mv '${tempFile}.new' '${tempFile}'`; break; } await execAsync(editCmd); // Generate diff const { stdout } = await execAsync(`diff -u '${file}' '${tempFile}' || true`); // Cleanup await execAsync(`rm -f '${tempFile}'`); return { content: [{ type: 'text', text: stdout ? `Preview of changes:\n${stdout}` : 'No changes would be made' }] }; }
- src/index.ts:203-226 (registration)Tool registration object including name, description, and input schema, added to the tools array for server.setTools().{ name: 'diff_preview', description: 'Preview what changes would be made by showing a diff', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'File to preview changes for' }, command: { type: 'string', description: 'Command that would make changes (e.g., "s/old/new/g")' }, tool: { type: 'string', enum: ['sed', 'perl', 'awk'], default: 'perl', description: 'Which tool to use for the preview' } }, required: ['file', 'command'] } },
- src/index.ts:207-224 (schema)Input schema defining the parameters for the diff_preview tool: file, command (required), and optional tool (perl/sed/awk).type: 'object', properties: { file: { type: 'string', description: 'File to preview changes for' }, command: { type: 'string', description: 'Command that would make changes (e.g., "s/old/new/g")' }, tool: { type: 'string', enum: ['sed', 'perl', 'awk'], default: 'perl', description: 'Which tool to use for the preview' } }, required: ['file', 'command']
- src/index.ts:493-511 (helper)Documentation and usage examples for the diff_preview tool in the helpContent object.diff_preview: `diff_preview - Preview changes ============================ See what changes would be made before applying. Examples: // Preview perl substitution diff_preview({ file: "config.json", command: "s/8080/3000/g" }) // Preview with sed syntax diff_preview({ file: "data.txt", command: "10,20d", tool: "sed" }) // Preview AWK processing diff_preview({ file: "log.csv", command: "BEGIN{FS=\",\"} {print $2}", tool: "awk" }) Output: - Shows unified diff format - No changes made to original file - Temp files are cleaned up `,