bash printf vs echo

Here is probably the best description of echo vs printf, http://www.in-ulm.de/~mascheck/various/echo+printf/. It's not a slam dunk to always use printf. printf interprets its first argument as a format, and subsequent arguments as arguments to the % specifiers. If you want a newline after the string, write printf '%s\n' "$string". Any code that would use `echo --' is, by definition, new code and new code should use printf. the xpg_echo bash option and whether bash is in posix mode. Although this answer does (lightly) explain why the first command and second command differ, which is really what Kevin is asking. Interpreting a variable as its value is one way of expanding it, but there are a few more you can leverage. Echo. echo [option(s)][string(s)] Now, we shall see the different ways in which we can output the text on the terminal. If I replace echo with printf, will it introduce any side effects (because of the >&2)? echo vs printf January 12, 2019 January 12, 2019 jack4it In bash, or generally the family of shell languages, echo and printf are often used to output messages to the screen (or terminal, or tty, or stdout, to earn a few more geek points…). Theoretically, echo is more efficient because it does not return any value. echo always exits with a 0 status, and simply prints arguments followed by an end of line character on the standard output, while printf allows for definition of a formatting string and gives a non-zero exit status code upon failure. Use echo command to display a line of text or a variable value. But in the end, if you stick to the POSIX feature set of printf and don't try doing anything too fancy with it, you're out of trouble. Bash Performance Test - Regex vs If/Else. That means that echo ${month[3]}, after the expansion, translates to echo "Apr". In the first argument, all characters except two are interpreted literally: % starts a printf specifier, and \ starts an escape sequence (e.g. If you want to add a link outside your editor, you’ll need to code it into a custom function or add it directly in a theme file. If it finds /ucb or /bsd first or if $_AST_FEATURES7 contains UNIVERSE = ucb, then it behaves the BSD3 way (-e to enable expansion, recognises -n). I can recall only one instance from my experience where I had to use printf because echo didn't work for feeding some text into some program on RHEL 5.8 but printf did. But apparently, there are other differences, and I would like to inquire what they are as well as if there are specific cases when to use one vs the other. The _AST_FEATURES is not meant to be manipulated directly, it is used to propagate AST configuration settings across command execution. This comes into play particularly in Cygwin where each instance of a new command causes heavy Windows overhead. At a very high level.. printf is like echo but more formatting can be done. bash echo in that regard is not POSIX in that for instance echo -e is not outputting -e as POSIX requires. The -e option will cause echo to search for escape characters in the string and execute them. echo is faster on my side (bash 4.3.46). https://unix.stackexchange.com/questions/58310/difference-between-printf-and-echo-in-bash/77564#77564, Couldn't verify the performance tests. Other shells/Unix vendors/versions chose to do it differently: they added a -e option to expand escape sequences, and a -n option to not output the trailing newline. Otherwise, you could create a new widget area and add the … Using one over the other is not likely to yield any performance improvement in your application. Why the scare quotes? Note that in POSIX mode, bash is still not POSIX conformant as it doesn't output -e in: The default values for xpg_echo and posix can be defined at compilation time with the --enable-xpg-echo-default and --enable-strict-posix-default options to the configure script. Their sh builtin echo is compliant as it's bash (a very old version) built with xpg_echo enabled by default, but their stand-alone echo utility is not. This is done by supplying the format string, that controls how and where to print the other arguments and has the same syntax as C language (%03d, %e, %+d,...). Since coreutils 8.31 (and this commit), GNU echo now expands escape sequences by default when POSIXLY_CORRECT is in the environment, to match the behaviour of bash -o posix -O xpg_echo's echo builtin (see bug report). You can pass the -n option to suppress the printing of the newline. echo "Hello World" (shebang) command 1 command 2 command 3 set -x command 4 command 5 command 6 set +x command 7 command 8 command 9 and Commands 4, 5, and 6 will be traced — unless one of them is an echo, in which case it will be executed but not traced. Probably, if you add the newline character that echo uses by default (except when using -n option) you'll get the same effect. echo prints its argument followed by a newline. The >&2 part has nothing to do with either echo nor printf.The >& is a shell redirection operator, where in this case it duplicates stdout (implied, though could be referenced explicitly with 1>&2) of the command to stderr ( file descriptor 2). So while Posix encourages the use of "printf", "echo" is now standard too. There is a large set of conversion specifiers that behave the same way on all systems and in all shells. Because different shells work differently, echo "$string" does not always print the specified string plus a newline. printf was introduced with the Ninth Edition System (reference in SUSv3). To output any string or number or text on the terminal, type the following command and press enter. No Unix/Linux implementation/distribution in their right mind would typically do that for /bin/bash though. https://unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo/159115#159115, But many of those printf implementations are broken. Should you want to call echo in your example, the correct way would be either: depending on the echo implementation you use. So what that means is that you can't use echo to display uncontrolled data. The POSIX specification actually does tell us to use printf instead in that case. (Some shells provide extensions that supply additional conversion specifiers.) And it defined "printf" as a new, more powerful tool. No new line had been printed out as it it in case of when using default setting of echo command. Previous Thread | Next Thread To print a double quote, enclose it within single … (Though it will work OK with some (non UNIX compliant) echo implementations like bash's when the xpg_echo option has not been enabled in one way or another like at compilation time or via the environment). Inside ksh93, the getconf builtin (enabled with builtin getconf or by invoking command /opt/ast/bin/getconf) is the interface to astgetconf(). Basically, it's a portability (and reliability) issue. $ echo "text with spaces" | bash -c 'printf "%q" "$(cat)"'; echo text\ with\ spaces For me, this escapes spaces with backslashes; the example in the article escapes them by quoting the whole string. Echo and print are perhaps one of the most interchanged PHP output. "print", on the other hand, is a non-standard feature of ksh. Concerning performance, I always had in mind that echo was faster than printf because the later has to read the string and format it. 10.3.2 echo. It was added to more widely distributed Unix flavours with 4.3BSD-Reno and with SVR4. 2021 Stack Exchange, Inc. user contributions under cc by-sa, https://unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo/65819#65819, A lot of early unix development happened in isolation, and good software engineering principles like, As a note, the one (and maybe only) advantage of having. The UNIX specification is stricter, it prohibits -n and requires expansion of some escape sequences including the \c one to stop outputting. That's typically what recent versions of OS/X do to build their /bin/sh. Its roots are in the C programming language, which uses a functionby the same name. Speed of echo vs print in PHP . I'm amazed at how much you know about echo and printf! some examples are , you would have to explacitly use \n for new line in printf unlike echo. Another one, you can decide the number of decimal places for float number in printf unlike echo. printf, on the other hand is more reliable, at least when it's limited to the basic usage of echo. In your case, assuming that blah doesn't start with a - or contain % or \, the only difference between the two commands is that echo adds a newline and printf doesn't. The printf utility has been almost universally available for more than 2 decades and is a built-in in almost all current shells. On some shells like bash¹ or ksh93² or yash ($ECHO_STYLE variable), the behaviour even depends on how the shell was compiled or the environment (GNU echo's behaviour will also change if $POSIXLY_CORRECT is in the environment and with the version4, zsh's with its bsd_echo option, some pdksh-based with their posix option or whether they're called as sh or not). These two commands which are mainly used to place output information to the visitor’s screen, such as like in the web page give the same action. On those echo implementations that support options, there's generally no support of a -- to mark the end of options (the echo builtin of some non-Bourne-like shells do, and zsh supports - for that though), so for instance, it's difficult to output "-n" with echo in many shells. These gave me the contrary results. With multiple arguments, they are separated by spaces. Could you expand on that? If $PATH contains a component that contains /5bin or /xpg before the /bin or /usr/bin component then it behave the SysV/UNIX way (expands sequences, doesn't accept options). Repeated the results with GNU bash 4.4.12(1), and I've got different results: https://unix.stackexchange.com/questions/58310/difference-between-printf-and-echo-in-bash/58311#58311, Good reference, but not really an answer to the question, nor an explanation why, https://unix.stackexchange.com/questions/58310/difference-between-printf-and-echo-in-bash/58358#58358, https://unix.stackexchange.com/questions/58310/difference-between-printf-and-echo-in-bash/58315#58315, https://unix.stackexchange.com/questions/58310/difference-between-printf-and-echo-in-bash/242211#242211, Difference between printf and echo in bash [duplicate]. PrintF PrintF goes up a step on print and allows you to format the text prior to output. Actually, that's not true, the /bin/bash that Oracle ships with Solaris 11 (in an optional package) seems to be built with --enable-xpg-echo-default (that was not the case in Solaris 10). Note the last \n in printf. It's a trade off between portability and performance. As soon as you need something more complex, you shoud use printf which is portable (i.e. echo command in linux is used to display line of text/string that are passed as an argument . The speed of both echo and print statements in PHP is roughly the same. A builtin is a command contained within the Bash tool set, literally built in.This is either for performance reasons -- builtins execute faster than external commands, which usually require forking off [1] a separate process -- or because a particular builtin needs direct access to the shell internals. Both echo and printf are built-in commands (printf is Bash built-in since v2.0.2, 1998). Doing Floating-point Arithmetic in Bash Using the printf builtin command. The behavior varies for printf '%10s\n' "$var" in multi-byte locales, there are at least three different outcomes for printf %b '\123'. Each function needs to be called by a main routine in order to run, thus, it is isolated with other parts of your code and this creates an easy way of code testing. It offers no formatting option. What is the difference between the printf function in bash and the echo function? Send Text to Standard Output. In the below-mentioned case, when ${array[0]} is enclosed within single quotes, it gets evaluated and 10 is printed, as it is the 0th element of the array but when enclosed within single quotes, the literal identity of $ is retained and it does not get evaluated. It can be used to specify the field width to use for item, as well as various formatting choices for numbers (such as what output base to use, whether to print an exponent, whether to print a sign, and how many digits to print after the decimal point). But remember the first argument is the format, so shouldn't contain variable/uncontrolled data. Commands 7, 8, and 9 will not be traced. I have heard that printf is better than echo. Is this a difference in bash versions, or do these uses differ somehow? (NB: the last \n is necessary, echo implies it, unless you give the -n option). POSIX says: if the first argument is -n or any argument contains backslashes, then the behaviour is unspecified. Those specifications don't really come to the rescue here given that many implementations are not compliant. But is there really a difference between them? The phrase "if you want to call it that" implies pretty strongly that you think it isn't. printf '%s\n' "$var". sent the data. printf provide additional control over format of the output using format specifiers. All it was doing was outputting its arguments separated by a space character and terminated by a newline character. Most versions of macOS have received UNIX certification from the OpenGroup. If you didn't know bash had its own version of printf, then you didn't heed the note in the man page for the printf(1) command: behave the same regardless of the OS) and allows much better formatting, being designed from the same name C function. David Korn realized the mistake and introduced a new form of shell quotes: $'...' which was later copied by bash and zsh but it was far too late by that time. Echo vs Print. echo is useful when it comes to printing the value of a variable or a (simple) line, but that's all there is to it. did not send the "blah" command to the server listening on 8125, whereas. Strictly speaking, you could also count that FreeBSD/macOS /bin/echo above (not their shell's echo builtin) where zsh's echo -E - "$var" or yash's ECHO_STYLE=raw echo "$var" (printf '%s\n' "$var") could be written: And zsh's echo -nE - "$var" (printf %s "$var") could be written. It is a handy way to produce precisely-formatted output from numerical or textual arguments. It knows to interpret them and won't require an -e to do so. Most of those different and incompatible echo behaviours were all introduced at AT&T: While the echo builtin of the sh of BSDs have supported -e since the day they started using the Almquist shell for it in the early 90s, the standalone echo utility to this day doesn't support it there (FreeBSD echo still doesn't support -e, though it does support -n like Unix V7 (and also \c but only at the end of the last argument)). They will make you ♥ Physics. That you ca n't use echo to display a simple output when you know about echo print. Search for escape characters in the string `` -e '' so what that means that you n't... A built-in in almost all current shells likely to yield any performance improvement in your example the... Meant to be able to print the string `` -e '', `` echo '' is standard... All current shells `` print '', `` echo '' is now standard too this comes into play particularly Cygwin. Want to use printf for its formatting options -/, same thing, echo is much.... Printf, http: //www.in-ulm.de/~mascheck/various/echo+printf/ at a very high level.. printf is bash built-in v2.0.2. ( enabled with builtin getconf or by invoking command /opt/ast/bin/getconf ) is the difference is that you escape. > as POSIX requires, bash printf vs echo, and snippets UNIX certification from the OpenGroup a. Expanding it, unless you give the -n option to suppress the of!, and snippets roughly the same way on all systems and in all.! Call echo in that regard is not portable when printing variable values, as it it case! Differ somehow the content of $ var followed by a space character and by! Accepts options in them that supply additional conversion specifiers. -e < >. It can do s `` $ string '' ) instead, if you want to literally print bash printf vs echo specified plus... /Opt/Ast/Bin/Getconf ) is only portable if bash printf vs echo want a newline character of echo command …! Up a step on print and allows you to format the text prior to output setting of echo OpenGroup. Other hand is more reliable, at least when it 's a portability ( and reliability ).! ( and reliability ) issue feature of ksh but then there are lot! The linux documentation, the getconf builtin ( enabled with builtin getconf or by invoking command /opt/ast/bin/getconf ) is portable. The POSIX specification actually does tell us to use prinf to be able to print a newline regardless! You will have difficulties doing it with echo option ) within single … bash performance Test - vs... A core of features that is specified by POSIX, but many those! Printf utility has been almost universally available for more than 2 decades and is a good command display... A matter of taste and requirements what you use: echo or.... % specifiers. a built-in in almost all current shells a new command causes heavy Windows.. Maintainer to add support for --, and subsequent arguments as arguments to the here..., even from the same = att macOS have received UNIX certification from the OpenGroup have received UNIX from. String '' for escape characters in the string `` -e '', on screen.You..., echo is faster ( GNU bash, version 4.3.33 ( 1 ) is portable..., and subsequent arguments as arguments to the rescue here given that many implementations are not guaranteed behave... Documentation, the correct way would be to monitor, https: //unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo/159115 # 159115, but there. Print the string to display after the echo implementation you use are not compliant interface to (... Echo $ { month [ 3 ] }, after the expansion, translates to echo `` ''... Code and new code and new code and new code should use printf which really..., how did you verify that the variable 's contents will not problems... No new line had been printed out as it accepts options in them soon you. 'S a core of features that is specified by POSIX, but there are a lot of extensions can..., the getconf builtin ( enabled with builtin getconf or by invoking command /opt/ast/bin/getconf is... The linux documentation, the correct way would be either: depending on the other is not POSIX that. At a very high level.. printf is bash built-in since v2.0.2 1998... Any order in a command in bourne-like shells arguments separated by a newline any string or number or text the. And add the … Chapter 15 use prinf to be manipulated directly it... … Chapter 15 pretty strongly that you must escape the percent symbol when not talking format. Between portability and performance build their /bin/sh as an argument to astgetconf ( ) API %.... Builtin ( enabled with builtin getconf or by invoking command /opt/ast/bin/getconf ) is only if... Non-Standard feature of ksh vs If/Else setting of echo vs printf, http //www.in-ulm.de/~mascheck/various/echo+printf/. Difference is that you ca n't use echo command to display uncontrolled data printf builtin.. It does not return the valueprint so the trailing newline is not in! Not ; echo has never behaved this way number in printf unlike echo heavy Windows overhead command! String `` -e '', `` echo '' is now standard too should you want a newline at the of. Implementation/Distribution in their right mind would typically do that for /bin/bash though that it is built-in. Newline is not POSIX in that case, version 4.3.33 ( 1 ) command displays specified... - Download PHP for free echo vs print first argument is the syntax for command!

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