PRINTF(1) User Commands PRINTF(1) NNAAMMEE printf - write formatted output SSYYNNOOPPSSIISS //uussrr//bbiinn//pprriinnttff pprriinnttff _f_o_r_m_a_t [_a_r_g_u_m_e_n_t]... kksshh9933 pprriinnttff _f_o_r_m_a_t [_s_t_r_i_n_g...] DDEESSCCRRIIPPTTIIOONN //uussrr//bbiinn//pprriinnttff The pprriinnttff utility writes each string operand to standard output using _f_o_r_m_a_t to control the output format. OOPPEERRAANNDDSS //uussrr//bbiinn//pprriinnttff The following operands are supported by //uussrr//bbiinn//pprriinnttff: _f_o_r_m_a_t A string describing the format to use to write the remaining operands. The _f_o_r_m_a_t operand is used as the _f_o_r_m_a_t string described on the ffoorrmmaattss(7) manual page, with the following exceptions: o A SSPPAACCEE character in the format string, in any context other than a flag of a conversion specification, is treated as an ordinary character that is copied to the output. o A character in the format string is treated as a character, not as a SSPPAACCEE character. o In addition to the escape sequences described on the ffoorrmmaattss(7) manual page (\\\\, \\aa, \\bb, \\ff, \\nn, \\rr, \\tt, \\vv), \\_d_d_d, where _d_d_d is a one-, two- or three-digit octal number, is written as a byte with the numeric value specified by the octal number. o The program does not precede or follow output from the dd or uu conversion specifications with blank characters not specified by the _f_o_r_m_a_t operand. o The program does not precede output from the oo conversion specification with zeros not specified by the _f_o_r_m_a_t operand. o The argument used for the conversion character (or width or precision parameters, see below) may be taken from the _nnth argument instead of the next unused argument, by specifying _n$$ immediately following the %% character, or the ** character (for width or precision arguments). If _n$$ appears in any conversions in the format string, then it must be used for all conversions, including any variable width or precision specifiers. o The special character ** may be used instead of a string of decimal digits to indicate a minimum field width or a precision. In this case the next available argument is used (or the _nth if the form _n$$ is used), treating its value as a decimal string. o An additional conversion character, bb, is supported as follows. The argument is taken to be a string that can contain backslash-escape sequences. The following backslash-escape sequences are supported: o the escape sequences listed on the ffoorrmmaattss(7) manual page (\\\\, \\aa, \\bb, \\ff, \\nn, \\rr, \\tt, \\vv), which are converted to the characters they represent o \\00_d_d_d, where _d_d_d is a zero-, one-, two- or three-digit octal number that is converted to a byte with the numeric value specified by the octal number o \\cc, which is written and causes pprriinnttff to ignore any remaining characters in the string operand containing it, any remaining string operands and any additional characters in the _f_o_r_m_a_t operand. The interpretation of a backslash followed by any other sequence of characters is unspecified. Bytes from the converted string are written until the end of the string or the number of bytes indicated by the precision specification is reached. If the precision is omitted, it is taken to be infinite, so all bytes up to the end of the converted string are written. For each specification that consumes an argument, the next argument operand is evaluated and converted to the appropriate type for the conversion as specified below. The _f_o_r_m_a_t operand is reused as often as necessary to satisfy the argument operands. Any extra cc or ss conversion specifications are evaluated as if a null string argument were supplied; other extra conversion specifications are evaluated as if a zero argument were supplied. When there are more argument operands than format specifiers, and the format includes _n$$ position indicators, then the format is reprocessed from the beginning as above, but with the argument list starting from the next argument after the highest _nth argument previously encountered. If the _f_o_r_m_a_t operand contains no conversion specifications and _a_r_g_u_m_e_n_t operands are present, the results are unspecified. If a character sequence in the _f_o_r_m_a_t operand begins with a %% character, but does not form a valid conversion specification, the behavior is unspecified. _a_r_g_u_m_e_n_t The strings to be written to standard output, under the control of ffoorrmmaatt. The _a_r_g_u_m_e_n_t operands are treated as strings if the corresponding conversion character is bb, cc or ss. Otherwise, it is evaluated as a C constant, as described by the ISO C standard, with the following extensions: o A leading plus or minus sign is allowed. o If the leading character is a single- or double- quote, the value is the numeric value in the underlying codeset of the character following the single- or double-quote. If an argument operand cannot be completely converted into an internal value appropriate to the corresponding conversion specification, a diagnostic message is written to standard error and the utility does not exit with a zero exit status, but continues processing any remaining operands and writes the value accumulated at the time the error was detected to standard output. kksshh9933 The _f_o_r_m_a_t operands support the full range of ANSI C/C99/XPG6 formatting specifiers as well as additional specifiers: %%bb Each character in the string operand is processed specially, as follows: \\aa Alert character. \\bb Backspace character. \\cc Terminate output without appending NEWLINE. The remaining string operands are ignored. \\EE Escape character (AASSCCIIII octal 003333). \\ff FORM FEED character. \\nn NEWLINE character. \\tt TAB character. \\vv Vertical tab character. \\\\ Backslash character. \\00_x The 8-bit character whose AASSCCIIII code is the 11-, 22-, or 33-digit octal number _x. %%BB Treat the argument as a variable name and output the value without converting it to a string. This is most useful for variables of type --bb. %%HH Output string with characters <<, &&, >>, "", and non-printable characters, properly escaped for use in HTML and XML documents. %%PP Treat _s_t_r_i_n_g as an extended regular expression and convert it to a shell pattern. %%qq Output _s_t_r_i_n_g quoted in a manner that it can be read in by the shell to get back the same string. However, empty strings resulting from missing string operands are not quoted. %%RR Treat _s_t_r_i_n_g as an shell pattern expression and convert it to an extended regular expression. %%TT Treat _s_t_r_i_n_g as a date/time string and format it. The TT can be preceded by (_d_f_o_r_m_a_t), where _d_f_o_r_m_a_t is a date format as defined by the ddaattee(1) command. %%ZZ Output a byte whose value is 00. When performing conversions of _s_t_r_i_n_g to satisfy a numeric format specifier, if the first character of _s_t_r_i_n_g is ""oorr'', the value is the numeric value in the underlying code set of the character following the ""oorr''. Otherwise, _s_t_r_i_n_g is treated like a shell arithmetic expression and evaluated. If a _s_t_r_i_n_g operand cannot be completely converted into a value appropriate for that format specifier, an error occurs, but remaining _s_t_r_i_n_g operands continue to be processed. In addition to the format specifier extensions, the following extensions of ANSI C/C99/XPG6 are permitted in format specifiers: o The escape sequences \\EE and \\ee expand to the escape character which is octal 033 in ASCII. o The escape sequence \\ccxx expands to CTRL-x. o The escape sequence \\CC[[.._n_a_m_e..]] expands to the collating element _n_a_m_e. o The escape sequence \\xx{{hheexx}} expands to the character corresponding to the hexadecimal value hheexx. o The format modifier flag = can be used to center a field to a specified width. When the output is a terminal, the character width is used rather than the number of bytes. o Each of the integral format specifiers can have a third modifier after width and precision that specifies the base of the conversion from 2 to 64. In this case, the ## modifier causes _b_a_s_e## to be prepended to the value. o The ## modifier can be used with the dd specifier when no base is specified to cause the output to be written in units of 1000 with a suffix of one of kk MM GG TT PP EE. o The ## modifier can be used with the ii specifier to cause the output to be written in units of 11002244 with a suffix of one of KKii MMii GGii TTii PPii EEii. If there are more _s_t_r_i_n_g operands than format specifiers, the format string is reprocessed from the beginning. If there are fewer _s_t_r_i_n_g operands than format specifiers, then _s_t_r_i_n_g specifiers are treated as if empty strings were supplied, numeric conversions are treated as if 00 was supplied, and time conversions are treated as if nnooww was supplied. When there are more argument operands than format specifiers, and the format includes _n$$ position indicators, then the format is reprocessed from the beginning as above, but with the argument list starting from the next argument after the highest _nth argument previously encountered. //uussrr//bbiinn//pprriinnttff is equivalent to kksshh9933's pprriinnttff built-in and pprriinntt --ff, which allows additional options to be specified. UUSSAAGGEE //uussrr//bbiinn//pprriinnttff The pprriinnttff utility, like the pprriinnttff(3C) function on which it is based, makes no special provision for dealing with multi-byte characters when using the %%cc conversion specification. Applications should be extremely cautious using either of these features when there are multi-byte characters in the character set. The %%bb conversion specification is not part of the ISO C standard; it has been added here as a portable way to process backslash escapes expanded in string operands as provided by the eecchhoo utility. See also the USAGE section of the eecchhoo(1) manual page for ways to use pprriinnttff as a replacement for all of the traditional versions of the eecchhoo utility. If an argument cannot be parsed correctly for the corresponding conversion specification, the pprriinnttff utility reports an error. Thus, overflow and extraneous characters at the end of an argument being used for a numeric conversion are to be reported as errors. It is not considered an error if an argument operand is not completely used for a cc or ss conversion or if a string operand's first or second character is used to get the numeric value of a character. EEXXAAMMPPLLEESS //uussrr//bbiinn//pprriinnttff EExxaammppllee 11 Printing a Series of Prompts The following example alerts the user, then prints and reads a series of prompts: example% pprriinnttff ""\\aaPPlleeaassee ffiillll iinn tthhee ffoolllloowwiinngg:: \\nnNNaammee:: "" rreeaadd nnaammee pprriinnttff ""PPhhoonnee nnuummbbeerr:: "" rreeaadd pphhoonnee EExxaammppllee 22 Printing a Table of Calculations The following example prints a table of calculations. It reads out a list of right and wrong answers from a file, calculates the percentage correctly, and prints them out. The numbers are right-justified and separated by a single tab character. The percentage is written to one decimal place of accuracy: example% wwhhiillee rreeaadd rriigghhtt wwrroonngg ;; ddoo ppeerrcceenntt==$$((eecchhoo ""ssccaallee==11;;(($$rriigghhtt**110000))//(($$rriigghhtt++$$wwrroonngg))"" || bbcc)) pprriinnttff ""%%22dd rriigghhtt\\tt%%22dd wwrroonngg\\tt((%%ss%%%%))\\nn"" \\ $$rriigghhtt $$wwrroonngg $$ppeerrcceenntt ddoonnee << ddaattaabbaassee__ffiillee EExxaammppllee 33 Printing number strings The command: example% pprriinnttff ""%%55dd%%44dd\\nn"" 11 2211 332211 44332211 5544332211 produces: 1 21 3214321 54321 0 The _f_o_r_m_a_t operand is used three times to print all of the given strings and that a 00 was supplied by pprriinnttff to satisfy the last %%44dd conversion specification. EExxaammppllee 44 Tabulating Conversion Errors The following example tabulates conversion errors. The pprriinnttff utility tells the user when conversion errors are detected while producing numeric output. These results would be expected on an implementation with 32-bit twos-complement integers when %%dd is specified as the _f_o_r_m_a_t operand: ┌───────────────────────────────────────────────────────────────────┐ │ Arguments Standard Diagnostic │ │5a 5 printf: 5a not completely converted │ │9999999999 2147483647 printf: 9999999999: Results too large │ │-9999999999 -2147483648 printf: -9999999999: Results too large │ │ABC 0 printf: ABC expected numeric value │ └───────────────────────────────────────────────────────────────────┘ The value shown on standard output is what would be expected as the return value from the function ssttrrttooll(3C). A similar correspondence exists between %%uu and ssttrrttoouull(3C), and %%ee, %%ff and %%gg and ssttrrttoodd(3C). EExxaammppllee 55 Printing Output for a Specific Locale The following example prints output for a specific locale. In a locale using the ISO/IEC 646:1991 standard as the underlying codeset, the command: example% pprriinnttff ""%%dd\\nn"" 33 ++33 --33 \\''33 \\""++33 ""''--33"" produces: ┌──────────────────────────────────┐ │33 Numeric value of constant 3 │ │33 Numeric value of constant 3 │ │−−33 Numeric value of constant −3 │ │5511 Numeric value of the │ │ character `3' in the ISO/IEC │ │ 646:1991 standard codeset │ │4433 Numeric value of the │ │ character `+' in the ISO/IEC │ │ 646:1991 standard codeset │ │4455 Numeric value of the │ │ character `−' in the SO/IEC │ │ 646:1991 standard codeset │ └──────────────────────────────────┘ In a locale with multi-byte characters, the value of a character is intended to be the value of the equivalent of the wwcchhaarr__tt representation of the character. If an argument operand cannot be completely converted into an internal value appropriate to the corresponding conversion specification, a diagnostic message is written to standard error and the utility does exit with a zero exit status, but continues processing any remaining operands and writes the value accumulated at the time the error was detected to standard output. EExxaammppllee 66 Alternative floating point representation 1 The pprriinnttff utility supports an alternative floating point representation (see pprriinnttff(3C) entry for the "%%aa"/"%%AA"), which allows the output of floating-point values in a format that avoids the usual base16 to base10 rounding errors. example% printf "%a\n" 2 3.1 NaN produces: 0x1.0000000000000000000000000000p+01 0x1.8ccccccccccccccccccccccccccdp+01 nan EExxaammppllee 77 Alternative floating point representation 2 The following example shows two different representations of the same floating-point value. example% x=2 ; printf "%f == %a\n" x x produces: 2.000000 == 0x1.0000000000000000000000000000p+01 EExxaammppllee 88 Output of unicode values The following command will print the EURO unicode symbol (code-point 0x20ac). example% LC_ALL=en_US.UTF-8 printf "[20ac]\n" produces: where "" represents the EURO currency symbol character. EExxaammppllee 99 Convert unicode character to unicode code-point value The following command will print the hexadecimal value of a given character. example% export LC_ALL=en_US.UTF-8 example% printf "%x\n" "'" where "" represents the EURO currency symbol character (code- point 0x20ac). produces: 20ac EExxaammppllee 1100 Print the numeric value of an ASCII character example% printf "%d\n" "'A" produces: 65 EExxaammppllee 1111 Print the language-independent date and time format To print the language-independent date and time format, the following statement could be used: example% printf "format" weekday month day hour min For example, $ printf format "Sunday" "July" 3 10 2 For American usage, format could be the string: "%s, %s %d, %d:%.2d\n" producing the message: Sunday, July 3, 10:02 Whereas for EU usage, format could be the string: "%1$s, %3$d. %2$s, %4$d:%5$.2d\n" Note that the '$' characters must be properly escaped, such as "%1\$s, %3\$d. %2\$s, %4\$d:%5\$.2d\n" in this case producing the message: Sunday, 3. July, 10:02 EENNVVIIRROONNMMEENNTT VVAARRIIAABBLLEESS See eennvviirroonn(7) for descriptions of the following environment variables that affect the execution of pprriinnttff: LLAANNGG, LLCC__AALLLL, LLCC__CCTTYYPPEE, LLCC__MMEESSSSAAGGEESS, LLCC__NNUUMMEERRIICC, and NNLLSSPPAATTHH. EEXXIITT SSTTAATTUUSS The following exit values are returned: 00 Successful completion. >>00 An error occurred. AATTTTRRIIBBUUTTEESS See aattttrriibbuutteess(7) for descriptions of the following attributes: //uussrr//bbiinn//pprriinnttff ┌────────────────────┬───────────────────┐ │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │ ├────────────────────┼───────────────────┤ │CSI │ Enabled │ ├────────────────────┼───────────────────┤ │Interface Stability │ Committed │ ├────────────────────┼───────────────────┤ │Standard │ See ssttaannddaarrddss(7). │ └────────────────────┴───────────────────┘ kksshh9933 ┌────────────────────┬─────────────────┐ │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │ ├────────────────────┼─────────────────┤ │Interface Stability │ Uncommitted │ └────────────────────┴─────────────────┘ SSEEEE AALLSSOO aawwkk(1), bbcc(1), ddaattee(1), eecchhoo(1), kksshh9933(1), pprriinnttff(3C), ssttrrttoodd(3C), ssttrrttooll(3C), ssttrrttoouull(3C), aattttrriibbuutteess(7), eennvviirroonn(7), ffoorrmmaattss(7), ssttaannddaarrddss(7) NNOOTTEESS Using format specifiers (characters following '%') which are not listed in the pprriinnttff(3C) or this manual page will result in undefined behavior. Using escape sequences (the character following a backslash ('\')) which are not listed in the pprriinnttff(3C) or this manual page will result in undefined behavior. Floating-point values follow C99, XPG6 and IEEE 754 standard behavior and can handle values the same way as the platform's |lloonngg ddoouubbllee| datatype. Floating-point values handle the sign separately which allows signs for values like NaN (for example, -nan), Infinite (for example, -inf) and zero (for example, -0.0). May 11, 2014 PRINTF(1)