#### 3.5.6 Scripting ¶

#### Comments ¶

The ‘`#`’ character introduces an end-of-line comment. All characters until and including the end of line are ignored.

#### Displaying Arbitrary Text ¶

The ‘`echo`’ (‘`ec`’) command prints its arguments to stdout.

#### Sourcing External Command Files ¶

The command ‘`source filename`’ reads commands from the named file. Its minimal abbreviation is ‘`so`’.

#### Setting and Unsetting the Variables ¶

The mail variables are set using ‘`set`’ (‘`se`’) command. The command takes a list of assignments. The syntax of an assignment is

‘`name=string`’

  Assign a string value to the variable. If string contains whitespace characters it must be enclosed in a pair of double-quote characters (‘`"`’)

‘`name=number`’

  Assign a numeric value to the variable.

‘`name`’

  Assign boolean `True` value.

‘`noname`’

  Assign boolean `False` value.

Example:

    ? set askcc nocrt indentprefix="> "

This statement sets `askcc` to `True`, `crt` to `False`, and `indentprefix` to “> ”.

To unset mail variables use ‘`unset`’(‘`uns`’) command. The command takes a list of variable names to unset.

To undo the effect of the previous example, do:

    ? unset askcc crt indentprefix

When used without arguments, both `set` or `unset` list all currently defined variables. The form of this listing is controlled by `variable-pretty-print` (`varpp`) variable. If it is set, a description precedes each variable, e.g.:

    # prompt user for subject before composing the message
    ask
    # prompt user for cc before composing the message
    askcc
    # output character set for decoded header fields
    charset="auto"
    # number of columns on terminal screen
    columns=80

If `variable-pretty-print` is not set, only the settings are shown, e.g.:

    ask
    askcc
    charset="auto"
    columns=80

A special command is provided to list all internal `mail` variables:

    variable [names...]

If used without arguments, it prints all known internal variables. If arguments are given, it displays only those internal variables that are listed in command line. For each variable, this command prints its name, data type, current value and a short description. For example:

    ? variable ask datefield
    ask, asksub
    Type: boolean
    Current value: yes
    prompt user for subject before composing the message

    datefield
    Type: boolean
    Current value: [not set]
    get date from the `Date:' header, instead of the envelope

#### Setting and Unsetting Shell Environment Variables ¶

Shell environment may be modified using ‘`setenv`’ (‘`sete`’) command. The command takes a list of assignments. The syntax of an assignment is:

‘`name=value`’

  If variable name does not already exist in the environment, then it is added to the environment with the value value. If name does exist, then its value in the environment is changed to value.

‘`name`’

  Delete the variable name from the environment (“unset” it).

#### Conditional Statements ¶

The conditional statement allows to execute a set of mail commands depending on the mode the `mail` program is in. The conditional statement is:

    if cond
    ...
    else
    ...
    endif

where ‘`...`’ represents the set of commands to be executed in each branch of the statement. cond can be one of the following:

‘`s`’

  True if `mail` is operating in mail sending mode.

‘`r`’

  True if `mail` is operating in mail reading mode.

‘`t`’

  True if stdout is a terminal device (as opposed to a regular file).

The conditional statements can be nested to arbitrary depth. The minimal abbreviations for ‘`if`’, ‘`else`’ and ‘`endif`’ commands are ‘`i`’, ‘`el`’ and ‘`en`’.

Example:

    if t
    set crt prompt="& "
    else
    unset prompt
    endif
    if s
    alt gray@example.com gray@example.org
    set