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printf
: Format and print dataprintf
does formatted printing of text. Synopsis:
printf format [argument]…
printf
prints the format string, interpreting ‘%’
directives and ‘\’ escapes to format numeric and string arguments
in a way that is mostly similar to the C ‘printf’ function.
See printf
format directives in The GNU C Library Reference Manual, for details.
The differences are listed below.
Due to shell aliases and built-in printf
functions, using an
unadorned printf
interactively or in a script may get you
different functionality than that described here. Invoke it via
env
(i.e., env printf …
) to avoid interference
from the shell.
printf
to produce no
further output. For example, the command ‘printf 'A%sC\cD%sF' B
E’ prints ‘ABC’.
ls --quoting=shell-escape
output.
POSIXLY_CORRECT
environment variable is set; otherwise, a
warning is printed. For example, ‘printf "%d" "'a"’ outputs
‘97’ on hosts that use the ASCII character set, since
‘a’ has the numeric value 97 in ASCII.
A floating-point argument must use a period before any fractional
digits, but is printed according to the LC_NUMERIC
category of the
current locale. For example, in a locale whose radix character is a
comma, the command ‘printf %g 3.14’ outputs ‘3,14’ whereas
the command ‘printf %g 3,14’ is an error.
See Floating point.
printf
interprets ‘\ooo’ in format as an octal number
(if ooo is 1 to 3 octal digits) specifying a byte to print,
and ‘\xhh’ as a hexadecimal number (if hh is 1 to 2 hex
digits) specifying a character to print.
Note however that when ‘\ooo’ specifies a number larger than 255,
printf
ignores the ninth bit.
For example, ‘printf '\400'’ is equivalent to ‘printf '\0'’.
printf
interprets two character syntaxes introduced in
ISO C 99:
‘\u’ for 16-bit Unicode (ISO/IEC 10646)
characters, specified as
four hexadecimal digits hhhh, and ‘\U’ for 32-bit Unicode
characters, specified as eight hexadecimal digits hhhhhhhh.
printf
outputs the Unicode characters
according to the LC_CTYPE
locale. Unicode characters in the ranges
U+0000…U+009F, U+D800…U+DFFF cannot be specified by this syntax,
except for U+0024 ($), U+0040 (@), and U+0060 ()`.
The processing of ‘\u’ and ‘\U’ requires a full-featured
iconv
facility. It is activated on systems with glibc 2.2 (or newer),
or when libiconv
is installed prior to this package. Otherwise
‘\u’ and ‘\U’ will print as-is.
The only options are a lone --help or --version. See Common options. Options must precede operands.
The Unicode character syntaxes are useful for writing strings in a locale independent way. For example, a string containing the Euro currency symbol
$ env printf '\u20AC 14.95'
will be output correctly in all locales supporting the Euro symbol (ISO-8859-15, UTF-8, and others). Similarly, a Chinese string
$ env printf '\u4e2d\u6587'
will be output correctly in all Chinese locales (GB2312, BIG5, UTF-8, etc).
Note that in these examples, the printf
command has been
invoked via env
to ensure that we run the program found via
your shell’s search path, and not a shell alias or a built-in function.
For larger strings, you don’t need to look up the hexadecimal code values of each character one by one. ASCII characters mixed with \u escape sequences is also known as the JAVA source file encoding. You can use GNU recode 3.5c (or newer) to convert strings to this encoding. Here is how to convert a piece of text into a shell script which will output this text in a locale-independent way:
$ LC_CTYPE=zh_CN.big5 /usr/local/bin/printf \ '\u4e2d\u6587\n' > sample.txt $ recode BIG5..JAVA < sample.txt \ | sed -e "s|^|/usr/local/bin/printf '|" -e "s|$|\\\\n'|" \ > sample.sh
An exit status of zero indicates success, and a nonzero value indicates failure.
Next: yes invocation, Previous: echo invocation, Up: Printing text [Contents][Index]