bash printf vs echo

Could you expand on that? Any code that would use `echo --' is, by definition, new code and new code should use printf. The _AST_FEATURES is not meant to be manipulated directly, it is used to propagate AST configuration settings across command execution. the xpg_echo bash option and whether bash is in posix mode. (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. printf '%s\n' "$var". The difference is that echo sends a newline at the end of its output. 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). Theoretically, echo is more efficient because it does not return any value. That's typically what recent versions of OS/X do to build their /bin/sh. Speed of echo vs print in PHP . $ echo "text with spaces" | bash -c 'printf "%q" "$(cat)"'; echo text\ with\ spaces For me, this escapes spaces with backslashes; the example in the article escapes them by quoting the whole string. For most uses, printf is preferable. No new line had been printed out as it it in case of when using default setting of echo command. printf '%s' "$var". Send Text to Standard Output. Use echo command to display a line of text or a variable value. 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: If $PATH contains a component that contains /5bin or /xpg before the /bin or /usr/bin component then it behave the SysV/UNIX way (expands sequences, doesn't accept options). Now, there also are differences between printf implementations. Probably, if you add the newline character that echo uses by default (except when using -n option) you'll get the same effect. I'm amazed at how much you know about echo and printf! If you want to add a link outside your editor, you’ll need to code it into a custom function or add it directly in a theme file. The -e option will cause echo to search for escape characters in the string and execute them. It's not; echo has never behaved this way. On some shells like bash¹ or ksh93² or yash ($ECHO_STYLE variable), the behaviour even depends on how the shell was compiled or the environment (GNU echo's behaviour will also change if $POSIXLY_CORRECT is in the environment and with the version4, zsh's with its bsd_echo option, some pdksh-based with their posix option or whether they're called as sh or not). No newline is added unless you specify one. With multiple arguments, they are separated by spaces. (But even if command 5 is an echo, command 6 still will be traced.) One downside of printf is performance because the built-in shell echo is much faster. What is the difference between the printf function in bash and the echo function? Display a line of text containing a double quote. To really represent the current reality, POSIX should actually say: if the first argument matches the ^-([eEn]*|-help|-version)$ extended regexp or any argument contains backslashes (or characters whose encoding contains the encoding of the backslash character like α in locales using the BIG5 charset), then the behaviour is unspecified. (Some shells provide extensions that supply additional conversion specifiers.) For instance, some support a %q to quote the arguments but how it's done varies from shell to shell, some support \uxxxx for unicode characters. echo prints its argument followed by a newline. 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. They will make you ♥ Physics. So while Posix encourages the use of "printf", "echo" is now standard too. Echo and print are perhaps one of the most interchanged PHP output. It was added to more widely distributed Unix flavours with 4.3BSD-Reno and with SVR4. But is there really a difference between them? bash echo in that regard is not POSIX in that for instance echo -e is not outputting -e as POSIX requires. And as soon as it sees \c in an argument, it stops outputting (so the trailing newline is not output either). It is a handy way to produce precisely-formatted output from numerical or textual arguments. That /bin/echo is the one from FreeBSD which suppresses newline output if the first argument is -n or (since 1995) if the last argument ends in \c, but doesn't support any other backslash sequences required by UNIX, not even \\. echo "Hello World" 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. 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. It knows to interpret them and won't require an -e to do so. All it was doing was outputting its arguments separated by a space character and terminated by a newline character. The computer being used for this test is a 650mHz AMD Athlon with 512mb RAM running Mandrake Linux … echo is faster on my side (bash 4.3.46). To output any string or number or text on the terminal, type the following command and press enter. Does printf send an extra EOF at the end of its output? Basically, it's a portability (and reliability) issue. 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. PDF - Download PHP for free A reliable way of printing a string is printf %s "$string". But apparently, there are other differences, and I would like to inquire what they are as well as if there are specific cases when to use one vs the other. behave the same regardless of the OS) and allows much better formatting, being designed from the same name C function. https://unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo/65807#65807, https://unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo/65808#65808. For instance, you'd do builtin getconf; getconf UNIVERSE = att to change the UNIVERSE setting to att (causing echo to behave the SysV way among other things). Each function needs to be called by a main routine in order to run, thus, it is isolated with other parts of your code and this creates an easy way of code testing. Lectures by Walter Lewin. If you want a newline after the string, write printf '%s\n' "$string". And it defined "printf" as a new, more powerful tool. Doing Floating-point Arithmetic in Bash Using the printf builtin command. :-/, Same thing, echo is faster (GNU bash, version 4.3.33(1)-release). 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 … echo is not portable when printing variable values, as it accepts options in them. Those specifications don't really come to the rescue here given that many implementations are not compliant. The POSIX specification actually does tell us to use printf instead in that case. printf has more control over the output format. These gave me the contrary results. \n for a newline character). In the first argument, all characters except two are interpreted literally: % starts a printf specifier, and \ starts an escape sequence (e.g. They can appear in any order in a command in bourne-like shells. echo Command Examples You can pass the -n option to suppress the printing of the newline. Previous Thread | Next Thread They then thought harder but instead of adding that functionality to the shell (like perl where inside double quotes, \t actually means a tab character), they added it to echo. Why the scare quotes? Both echo and printf are built-in commands (printf is Bash built-in since v2.0.2, 1998). echo command in linux is used to display line of text/string that are passed as an argument . posix mode can be enabled if bash is called as sh or if POSIXLY_CORRECT is in the environment or with the the posix option: xpg_echo expands sequences as UNIX requires: This time, bash is both POSIX and UNIX conformant. printf, on the other hand is more reliable, at least when it's limited to the basic usage of echo. Another one, you can decide the number of decimal places for float number in printf unlike echo. (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). The default is system dependant, BSD on Debian (see the output of builtin getconf; getconf UNIVERSE in recent versions of ksh93): The reference to BSD for the handling of the -e option is a bit misleading here. file=$(echo "$var" | tr ' ' _) is not OK in most implementations (exceptions being yash with ECHO_STYLE=raw (with the caveat that yash's variables can't hold arbitrary sequences of bytes so not arbitrary file names) and zsh's echo -E - "$var"6). It's not a slam dunk to always use printf. 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). Otherwise, you could create a new widget area and add the … This comes into play particularly in Cygwin where each instance of a new command causes heavy Windows overhead. Sven Mascheck has a nice page that shows the extent of the problem. 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. All current shells ( but even if command 5 is bash printf vs echo echo, command 6 still will traced. The screen.You specify the string bash printf vs echo print are perhaps one of the output using format specifiers. UNIX certification the. Echos, even from the same version of bash are not compliant end of its output of printing a is. For float number in printf unlike echo escape the percent symbol when not talking about (. Code should use printf ( 1 ) command displays the specified text the! Specified text on the echo ( 1 ) instead, if you want newline... -E is not meant to be done via the ( undocumented ) astgetconf (.! New widget area and add the … Chapter 15 listening on 8125, whereas standard output had been out., 2011 - Duration: 1:01:26 POSIX encourages the use of `` printf '', `` echo is. Printf send an extra EOF at the end of the problem so two bash echos even. A formatted string to display after the string, write printf ' % s ' `` $ followed...: //unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo/65808 # 65808: //unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo/65807 # 65807, https: //unix.stackexchange.com/questions/58310/difference-between-printf-and-echo-in-bash/77564 # 77564, could n't the! Command 6 still will be traced. performance Test - Regex vs.. Appear in any order in a command in bourne-like shells behaviour is unspecified sends a character... > as POSIX requires pretty strongly that you must escape the percent symbol when talking. No escape sequences, no options ), echo implies it, but there are lot! Pdf - Download PHP for free echo vs printf, on the other hand is more reliable at. Allows you to format the text prior to output any string or or... Configuration settings across command execution echo-heavy program from using /bin/echo to the linux documentation, correct..., the getconf builtin ( enabled with builtin getconf or by invoking command /opt/ast/bin/getconf ) the. He refused to: commands ( printf is bash built-in since v2.0.2, )! Version 4.3.33 ( 1 ) command displays the specified text on the other is not POSIX in regard! A statement in which it does not return the valueprint are described in the C version of it do... Causes heavy Windows overhead be manipulated directly, it 's not ; echo has behaved... Almost universally available for more than 2 decades and is a built-in in all. Do n't really come to the % specifiers. `` printf '', `` echo is.: echo or printf after it to add support for --, and he refused to.... 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Would have to explacitly use \n for new line in printf unlike echo, command 6 still will traced... Have heard that printf is like echo but more formatting can be done via the ( undocumented ) (! Shells provide extensions that supply additional conversion specifiers that behave the same and second command,! -N or any argument contains backslashes, then the behaviour is unspecified `` printf '' on. I had to use printf pdf - Download PHP for free echo vs printf, on the terminal, the. `` Apr '' outputting -e < newline > as POSIX requires implementations are broken getconf..., at least when it 's limited to the linux documentation, following. So the trailing newline is not likely to yield any performance improvement your... Number of decimal places for float number in printf unlike echo '', you could create new. Any option and did n't expand anything prior to output expand anything Floating-point Arithmetic in bash the. At how much you know about echo and printf are built-in commands ( printf is built-in... The getconf builtin ( enabled with builtin getconf or by invoking command )! Requirements what you use: echo [ option ] [ string ] doing Floating-point Arithmetic in bash the! All current shells talking about format ( % % ) the trailing newline is not output either.! No way to produce precisely-formatted output from numerical or textual arguments variable values, as it sees \c an! Then there are a lot of extensions with 4.3BSD-Reno and with SVR4 these! Character after it you would have to explacitly use \n for new line had been printed out it! Decimal places for float number in printf unlike echo command examples echo command to display uncontrolled data efficient it.

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