Magic Commands

Magic commands are REPL-only shortcuts prefixed with %. They provide quick access to common operations without parentheses or string quotes.

%cd <dir>

Change the current working directory.

%cd /tmp
%pwd      -- /tmp
%cd ~     -- expands ~ correctly

If the directory does not exist, an error message is printed. The shell escape ?<{cd ...}> also changes the T interpreter’s working directory via the same mechanism.

%env

Print all environment variables, one per line.

%env
HOME=/home/user
PATH=/usr/bin:/bin
...

%history

Show the last 50 entries from the REPL command history (~/.t_history).

%history
    1  x = 42
    2  y = x + 1
    3  %pwd

If no history exists, displays (no history).

%ls

List files and directories in the current working directory.

%ls
file1.t  file2.t  data.csv

%magic

List all available magic commands with descriptions.

%magic

Equivalent to the :help section on magic commands.

%objects

List all user-defined variables, their types, and a compact summary.

x = 42
df = read_csv("data.csv")
%objects
--  name  type       summary
--  x     Int        42
--  df    DataFrame  150 rows x 5 cols

Alias: %who.

%pwd

Print the current working directory.

%pwd
/home/user/projects

%reset

Remove all user-defined variables and return to the clean base environment. Also clears the session transcript for %save.

x = 42
%reset
%objects
-- (no user objects)

%save <file> / %save verbose <file>

Save a session transcript — every command and its result — to a file. Each entry is written as # command followed by # result.

Compact mode (%save file.t) uses value_summary:

# x = 42
# 42

# read_csv("data.csv")
# DataFrame: 150 rows x 5 cols

Verbose mode (%save verbose file.t) uses the full pretty-printed output:

# x = 42
# 42

# read_csv("data.csv")
# ┌──────┬──────┐
# │ col1 │ col2 │
# ├──────┼──────┤
# │ ...  │ ...  │
# └──────┴──────┘

Can be combined with %reset to start a fresh transcript before recording.

%time <expr>

Evaluate any T expression and print its result along with execution time.

%time 1 + 1
2
Execution time: 0.0002 seconds

%time df |> filter($x > 10) |> nrow()
42
Execution time: 0.1540 seconds

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Quick Reference

Command	Description
%cd <dir>	Change directory
%env	List environment variables
%history	Show command history
%ls	List directory contents
%magic	List magic commands
%objects / %who	List user-defined objects
%pwd	Print working directory
%reset	Reset environment to base
%save <file>	Save session transcript (compact)
%save verbose <file>	Save session transcript (verbose)
%time <expr>	Time an expression

Typing an unknown magic command triggers fuzzy matching: %objcts suggests Did you mean: %objects?.