User Commands read(1)
NAME
read - read a line from standard input
SYNOPSIS
/usr/bin/read [-r] var...
sh
read name...
csh
set variable= $<
ksh
read [-prsu [n] [name ? prompt] [name]...
ksh93
read [-Aprs] [-d delim] [-n nsize] [-N nsize] [-t timeout][-u unit] [vname?prompt] [vname... ]
DESCRIPTION
/usr/bin/read
The read utility reads a single line from standard input.
By default, unless the -r option is specified, backslash (\)
acts as an escape character. If standard input is a terminal
device and the invoking shell is interactive, read prompts
for a continuation line when:
o The shell reads an input line ending with a
backslash, unless the -r option is specified.
o A here-document is not terminated after a NEWLINE
character is entered.
The line is split into fields as in the shell. The first
field is assigned to the first variable var, the second
field to the second variable var, and so forth. If there are
fewer var operands specified than there are fields, the
leftover fields and their intervening separators is assigned
to the last var. If there are fewer fields than vars, the
remaining vars is set to empty strings.
The setting of variables specified by the var operands
affects the current shell execution environment. If it is
called in a sub-shell or separate utility execution
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User Commands read(1)
environment, such as one of the following:
(read foo)
nohup read ...
find . -exec read ... \;
it does not affect the shell variables in the caller's
environment.
The standard input must be a text file.
sh
One line is read from the standard input and, using the
internal field separator, IFS (normally space or tab), to
delimit word boundaries, the first word is assigned to the
first name, the second word to the second name, and so on,
with leftover words assigned to the last name. Lines can be
continued using \newline. Characters other than NEWLINE can
be quoted by preceding them with a backslash. These
backslashes are removed before words are assigned to names,
and no interpretation is done on the character that follows
the backslash. The return code is 0, unless an end-of-file
is encountered.
csh
The notation:
set variable = $<
loads one line of standard input as the value for variable.
(See csh(1)).
ksh
The shell input mechanism. One line is read and is broken up
into fields using the characters in IFS as separators. The
escape character, (\), is used to remove any special meaning
for the next character and for line continuation. In raw
mode, the -r, the , and the \ character are not treated spe-
cially. The first field is assigned to the first name, the
second field to the second name, and so on, with leftover
fields assigned to the last name. The -p option causes the
input line to be taken from the input pipe of a process
spawned by the shell using &. If the -s flag is present,
the input is saved as a command in the history file. The
flag -u can be used to specify a one digit file descriptor
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User Commands read(1)
unit n to read from. The file descriptor can be opened with
the exec special command. The default value of n is 0. If
name is omitted, REPLY is used as the default name. The exit
status is 0 unless the input file is not open for reading or
an end-of-file is encountered. An end-of-file with the -p
option causes cleanup for this process so that another can
be spawned. If the first argument contains a ?, the
remainder of this word is used as a prompt on standard error
when the shell is interactive. The exit status is 0 unless
an end-of-file is encountered.
ksh93
read reads a line from standard input and breaks it into
fields using the characters in the value of the IFS variable
as separators. The escape character, \, is used to remove
any special meaning for the next character and for line con-
tinuation unless the -r option is specified.
If there are more variables than fields, the remaining vari-
ables are set to empty strings. If there are fewer variables
than fields, the leftover fields and their intervening
separators are assigned to the last variable. If no var is
specified, the variable REPLY is used.
When var has the binary attribute and -n or -N is specified,
the bytes that are read are stored directly into var.
If you specify ?prompt after the first var, read displays a
prompt on standard error when standard input is a terminal
or pipe.
OPTIONS
/usr/bin/read, ksh
The following option is supported by /usr/bin/read and ksh:
-r Do not treat a backslash character in any special way.
Considers each backslash to be part of the input line.
ksh93
The following options are supported by ksh93:
-A Unset var, and create an indexed array con-
taining each field in the line starting at
index 0.
-d delim Read until delimiter delim instead of to the
end of line.
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User Commands read(1)
-n nsize Read at most nsize bytes. Binary field size is
in bytes.
-N nsize Read exactly nsize bytes. Binary field size is
in bytes.
-p Read from the current co-process instead of
standard input. An end of file causes read to
disconnect the co-process so that another can
be created.
-r Do not treat \ specially when processing the
input line.
-s Save a copy of the input as an entry in the
shell history file.
-t timeout Specify a timeout in seconds when reading from
a terminal or pipe.
-u fd Read from file descriptor number fd instead of
standard input. The default value is 0.
-v When reading from a terminal, display the
value of the first variable and use it as a
default value.
OPERANDS
The following operand is supported:
var The name of an existing or non-existing shell vari-
able.
EXAMPLES
Example 1 Using the read Command
The following example for /usr/bin/read prints a file with
the first field of each line moved to the end of the line:
example% while read -r xx yy
do
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User Commands read(1)
printf "%s %s\n" "$yy" "$xx"
done < inputfile
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment
variables that affect the execution of read: LANG, LCAL,
LCTYPE, LCMESAGES, and NLSPATH.
IFS Determines the internal field separators used to del-
imit fields.
PS2 Provides the prompt string that an interactive shell
writes to standard error when a line ending with a
backslash is read and the -r option was not speci-
fied, or if a here-document is not terminated after a
NEWLINE character is entered.
EXIT STATUS
The following exit values are returned:
0 Successful completion.
>0 End-of-file was detected or an error occurred.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
/usr/bin/read, csh, ksh, sh
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWcsu
Interface Stability Committed
Standard See standards(5).
ksh93
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User Commands read(1)
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWcsu
Interface Stability Uncommitted
SEE ALSO
csh(1), ksh(1), ksh93(1), line(1), set(1), sh(1), attri-
butes(5), environ(5), standards(5)
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