echo - Print Text

Write arguments to standard output.

Source: src/execution/builtins.f90:builtin_echo

Synopsis

echo [-neE] [arguments...]

Description

Outputs its arguments separated by spaces, followed by a newline. The echo builtin is POSIX-compliant by default: escape sequences are NOT interpreted unless -e is specified.

Options

Option	Description
`-n`	Do not print trailing newline
`-e`	Interpret backslash escape sequences
`-E`	Do not interpret escape sequences (default)

Options can be combined: -ne, -en, -nE

Escape Sequences (with -e)

Sequence	Character
`\a`	Alert (bell, ASCII 7)
`\b`	Backspace (ASCII 8)
`\c`	Stop output (suppress newline and remaining text)
`\f`	Form feed (ASCII 12)
`\n`	Newline
`\r`	Carriage return (ASCII 13)
`\t`	Horizontal tab (ASCII 9)
`\v`	Vertical tab (ASCII 11)
`\\`	Literal backslash

Return Value

Code	Meaning
0	Success
1	Write error

Examples

Basic output

echo Hello, World!
# Output: Hello, World!

No newline

echo -n "Enter name: "
read name

Escape sequences

echo -e "Line 1\nLine 2"
# Output:
# Line 1
# Line 2

echo -e "Column1\tColumn2"
# Output: Column1	Column2

echo -e "Bell: \a"  # System bell

Stop output

echo -e "This prints\c but this doesn't"
# Output: This prints

Combined options

echo -en "Loading...\r"
# Prints without newline, returns cursor to start

Implementation Details

From builtins.f90:

! Parse flags at start
do while (arg_index <= num_args)
    arg = args(arg_index)
    if (arg == "-n") then
        add_newline = .false.
    else if (arg == "-e") then
        interpret_escapes = .true.
    else if (arg == "-E") then
        interpret_escapes = .false.
    else if (arg == "-ne" .or. arg == "-en") then
        add_newline = .false.
        interpret_escapes = .true.

The escape sequence processor handles each sequence character-by-character:

case ('n')
    output(out_pos:out_pos) = char(10)  ! newline
case ('t')
    output(out_pos:out_pos) = char(9)   ! tab
case ('c')
    exit  ! stop processing

POSIX Compliance

fortsh's echo follows POSIX behavior:

Escape sequences are NOT interpreted by default
Use -e to enable escape interpretation
Some shells (like bash in non-POSIX mode) interpret escapes by default

For portable scripts, prefer printf which has consistent behavior across shells.

Related Commands

printf - Formatted output (more portable)
read - Read input

Notes

Empty arguments are preserved when quoted: echo "" "" outputs two empty strings
Arguments are separated by single spaces regardless of input whitespace
Uses file descriptor-aware I/O, respecting redirections