$ltrim (Trim Left)
Last updated: 2026-10-09
$ltrim (Trim Left)
$ltrim strips whitespace, or characters in the given chars set, from the left (start) of a string — the left-side variant of $trim. Handy for leading spaces, indentation, or prefix symbols. chars defaults to whitespace; a custom set overrides it. Null or missing input yields null. Combining $ltrim with $rtrim emulates $trim.
| Category | String |
|---|---|
| MongoDB Version | 1.0+ |
| Example Language | mongosh (Shell) |
📝 Syntax
{ $ltrim: { input: <string-expression>, chars: <charset> } }⚙️ Parameters
| input | Required; the string to process. |
|---|---|
| chars | Optional custom charset; whitespace by default. |
Returns：The left-trimmed string; null if input is null.
▶ Example
Run the commands below in your local mongosh (requires a running mongod):
// $ltrim: strip leading whitespace from log lines
db.logs.aggregate([
{ $project: { msg: { $ltrim: { input: '$raw' } } } }
])Output：
{ "_id": 1, "msg": "server started" }
{ "_id": 2, "msg": "timeout" }📌 Notes
- Left end only; the right end stays untouched
- chars defaults to the whitespace set
- Combined with $rtrim it emulates $trim
🏷️ Related Tags
💡 Related Cases
More hands-on cases coming soon.
📚 Related Tutorials
❓ FAQ
QDoes it only strip the left side?
AYes — $ltrim only strips the start of the string.
QWhat if the right side also has spaces?
AFollow with $rtrim, or just use $trim in one call.
QCan custom characters be stripped?
AYes — specify them via chars.
