Specifications

Version 2.0

2>>v Append standard error to an environment variable, encoded as UCS2.

The UEFI Shell will redirect standard output to a single file or variable and standard

error to a single file or variable. Redirecting both standard output and standard error

to different files or variables is allowed, but not to the same file or variable.

Redirecting standard output to more than one file or variable on the same command is

not supported. Similarly, redirecting to multiple files or variables is not supported for

standard error either.

When redirecting output to an environment variable, if a new environment variable

will be created, then it will be volatile. If the environment variable already exists and

is non-volatile, an error will be generated.

All output to UCS-2 encoded files will be prefixed with the Unicode Byte Ordering

Character (0xFFFE) if (a) there is at least one other character output and (b) that

character is not the Unicode Byte Ordering Character.

“NUL” is used as a special output file name. When “NUL” is used, the output will not be

written into a file. Instead, they are discarded silently.

3.4.4.2 Input Redirection

Contents from an existing file or variable can be used as standard input to a UEFI

shell command. Any commands coming from an ASCII file will be automatically be

converted to the equivalent UCS-2 encoding and passed to the UEFI shell command.

When redirecting input from an environment variable, the environment variable must

already exist. If it does not, an error will be generated. The shell will ensure that the

first character read from an input redirected environment variable will contain the

Unicode Byte Ordering Character (0xFFFE). If the first character in the input source is

not the Unicode Byte Ordering Character, the shell will insert this character in the

output from the input redirected variable. This is done to ensure that an input

redirected variable will be look like a UCS-2 encoded file.

Redirecting input from a non-volatile variable is permitted.

Table 5 Input Redirection Syntax

Character Sequence Description

< Redirect standard input from a Unicode file.

<a Redirect standard input from an ASCII file.

<v Redirect standard input from an environment variable.

3.4.4.3 Pipe Support

By using the | character, a data channel is formed that takes the standard Unicode

output of a file and feeds the data as standard input to another program.

The format for this support is as follows: