Echo (command): Difference between revisions
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In [[computing]], '''<code>echo</code>''' is a [[command (computing)|command]] that outputs the strings |
In [[computing]], '''<code>echo</code>''' is a [[command (computing)|command]] that outputs the strings that are passed to it as [[command-line argument|arguments]]. It is a command available in various [[operating system]] [[shell (computing)|shells]] and typically used in [[shell script]]s and [[batch file]]s to output status text to the screen<ref name="rugheimer-spanik-amigados" /> or a [[computer file]], or as a source part of a [[Pipeline (Unix)|pipeline]]. |
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==Implementations== |
==Implementations== |
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The command is available in the following operating systems: |
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The command is available in [[Multics]],<ref>{{Cite web|url=https://www.multicians.org/multics-commands.html|title=Multics Commands|website=www.multicians.org}}</ref> [[Technical Systems Consultants|TSC]] [[FLEX (operating system)|FLEX]],<ref>{{Cite web|url=http://www.flexusergroup.com/flexusergroup/pdfs/swflexum.pdf|title=FLEX 9.0 User's Manual}}</ref> [[MetaComCo]] [[TRIPOS]],<ref>{{cite web |url=https://www.pagetable.com/docs/amigados_tripos/tripos_manuals.pdf |title= Manual |website=www.pagetable.com|access-date=2020-09-12}}</ref> [[Zilog]] [[Z80-RIO]],<ref>[https://www.z80cpu.eu/mirrors/oldcomputers.dyndns.org/public/pub/rechner/zilog/zds/z80-rio_os_userman.pdf Z80-RIO OPERATING SYSTEM USER'S MANUAL]</ref> [[Microware]] [[OS-9]],<ref>{{cite book|author=Paul S. Dayan|year=1992|title=The OS-9 Guru - 1 : The Facts|publisher=Galactic Industrial Limited|isbn=0-9519228-0-7}}</ref> [[DOS]], [[Acorn Computers]] [[Panos (operating system)|Panos]],<ref>{{Cite web|url=http://chrisacorns.computinghistory.org.uk/Panos.html#CL|title=Chris's Acorns: Panos|website=chrisacorns.computinghistory.org.uk}}</ref> [[Digital Research]] [[FlexOS]],<ref>[http://www.bitsavers.org/pdf/digitalResearch/flexos/1073-2003_FlexOS_Users_Guide_V1.3_Nov86.pdf]{{dead link|date=September 2020}}</ref> [[IBM]] [[OS/2]],<ref>[http://www.jatomes.com/Help/Os2Bat.php#ECHO]{{dead link|date=September 2020}}</ref> [[Microsoft Windows]],<ref>{{Cite web|url=https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/echo|title=echo|website=docs.microsoft.com}}</ref> [[ReactOS]],<ref>{{Cite web|url=https://github.com/reactos/reactos|title=reactos/reactos|website=GitHub}}</ref> [[Hewlett-Packard|HP]] [[HP Multi-Programming Executive|MPE/iX]],<ref>[http://www.teamnaconsulting.com/compresources/pdfs/c01687363.pdf MPE/iX Command Reference Manual]</ref> [[KolibriOS]],<ref>{{Cite web|url=http://wiki.kolibrios.org/wiki/Shell|title=Shell - KolibriOS wiki|website=wiki.kolibrios.org}}</ref> [[SymbOS]], [[Unix]] and [[Unix-like]] operating systems. |
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* [[Multics]]<ref name="multics" /> |
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* [[Technical Systems Consultants|TSC]] [[FLEX (operating system)|FLEX]]<ref name="flexusergroup" /> |
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* [[MetaComCo]] [[TRIPOS]]<ref name="tripos" /> |
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* [[Zilog]] [[Z80-RIO]]<ref name="z80 user guide" /> |
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* [[Microware]] [[OS-9]]<ref name="os-9 guru" /> |
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* [[DOS]] |
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* [[Acorn Computers]] [[Panos (operating system)|Panos]]<ref name="computinghistory" /> |
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* [[Digital Research]] [[FlexOS]]<ref name="flexos user guide" /> |
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* [[IBM]] [[OS/2]]<ref name="jatomes" /> |
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* [[Microsoft Windows]]<ref name="windows-commands" /> |
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* [[ReactOS]]<ref name="reactos" /> |
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* [[Hewlett-Packard|HP]] [[HP Multi-Programming Executive|MPE/iX]]<ref name="teamnaconsulting" /> |
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* [[KolibriOS]]<ref name="kolibrios" /> |
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* [[SymbOS]] |
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* [[Unix]] and [[Unix-like]] operating systems |
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Many shells, including all [[Bourne shell|Bourne]]-like (such as [[Bash (Unix shell)|Bash]]<ref |
Many shells, including all [[Bourne shell|Bourne]]-like (such as [[Bash (Unix shell)|Bash]]<ref name="Bash-Builtins" /> or [[zsh]]<ref name="zsh echo" />) and [[C shell|Csh]]-like shells as well as [[COMMAND.COM]] and [[cmd.exe]] implement <code>echo</code> as a [[shell builtin|builtin command]]. |
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The command is also available in the [[Unified Extensible Firmware Interface|EFI shell]].<ref name="EFI-Shells-and-Scripting" |
The command is also available in the [[Unified Extensible Firmware Interface|EFI shell]].<ref name="EFI-Shells-and-Scripting" /> |
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==History== |
==History== |
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<code>echo</code> began within [[Multics]]. After it was programmed in [[C (programming language)|C]] by [[Douglas McIlroy|Doug McIlroy]] as a "finger exercise" and proved to be useful, it became part of [[Version 2 Unix]]. <code>echo -n</code> in [[Version 7 Unix|Version 7]] replaced <code>prompt</code>, (which behaved like <code>echo</code> but without terminating its output with a line delimiter).<ref name="reader" |
<code>echo</code> began within [[Multics]]. After it was programmed in [[C (programming language)|C]] by [[Douglas McIlroy|Doug McIlroy]] as a "finger exercise" and proved to be useful, it became part of [[Version 2 Unix]]. <code>echo -n</code> in [[Version 7 Unix|Version 7]] replaced <code>prompt</code>, (which behaved like <code>echo</code> but without terminating its output with a line delimiter).<ref name="reader" /> |
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On [[PWB/UNIX]] and later [[Unix System III]], <code>echo</code> started expanding [[Escape sequences in C|C escape sequences]] such as <code>\n</code> with the notable difference that octal escape sequences were expressed as <code>\0ooo</code> instead of <code>\ooo</code> in C.<ref name="mascheck-echo" |
On [[PWB/UNIX]] and later [[Unix System III]], <code>echo</code> started expanding [[Escape sequences in C|C escape sequences]] such as <code>\n</code> with the notable difference that octal escape sequences were expressed as <code>\0ooo</code> instead of <code>\ooo</code> in C.<ref name="mascheck-echo" /> |
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[[Research Unix|Eighth Edition Unix]] <code>echo</code> only did the escape expansion when passed a <code>-e</code> option,<ref |
[[Research Unix|Eighth Edition Unix]] <code>echo</code> only did the escape expansion when passed a <code>-e</code> option,<ref name="man echo" /> and that behaviour was copied by a few other implementations such as the builtin <code>echo</code> command of [[Bash (Unix shell)|Bash]] or [[zsh]] and GNU <code>echo</code>. |
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On [[MS-DOS]], the command is available in versions 2 and later.<ref name="RUNNINGMSDOS" |
On [[MS-DOS]], the command is available in versions 2 and later.<ref name="RUNNINGMSDOS" /> |
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Nowadays, several incompatible implementations of <code>echo</code> exist on different operating systems (often several on the same system), some of them expanding escape sequences by default, some of them not, some of them accepting options (the list of which varying with implementations), some of them not. |
Nowadays, several incompatible implementations of <code>echo</code> exist on different operating systems (often several on the same system), some of them expanding escape sequences by default, some of them not, some of them accepting options (the list of which varying with implementations), some of them not. |
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The [[POSIX]] Specification of <code>echo</code><ref>{{man|cu|echo|SUS|write arguments to standard output}}</ref> leaves the behaviour unspecified if the first argument is <code>-n</code> or any argument contain backslash characters while the Unix specification (XSI option in POSIX) mandates the expansion of (some) sequences and does not allow any option processing. In practice, many <code>echo</code> implementations are not compliant in the default environment. |
The [[POSIX]] Specification of <code>echo</code><ref>{{man|cu|echo|SUS|write arguments to standard output}}</ref> leaves the behaviour unspecified if the first argument is <code>-n</code> or any argument contain backslash characters while the Unix specification (XSI option in POSIX) mandates the expansion of (some) sequences and does not allow any option processing. In practice, many <code>echo</code> implementations are not compliant in the default environment. |
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Because of these variations in behaviour, <code>echo</code> is considered a non-portable command on Unix-like systems<ref |
Because of these variations in behaviour, <code>echo</code> is considered a non-portable command on Unix-like systems<ref name="echo limitations" /> and the [[printf (Unix)|<code>printf</code> command]] (where available, introduced by Ninth Edition Unix) is preferred instead. |
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==Usage examples== |
==Usage examples== |
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==See also== |
==See also== |
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*[[List of Unix commands]] |
* [[List of Unix commands]] |
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*[[List of DOS commands]] |
* [[List of DOS commands]] |
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==References== |
==References== |
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{{Reflist |
{{Reflist|refs= |
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<ref name="EFI-Shells-and-Scripting">{{cite web |
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<ref name="mascheck-echo">{{cite web|last1=Mascheck|first1=Sven|title=echo and printf behaviour|url=http://www.in-ulm.de/~mascheck/various/echo+printf/|access-date=24 July 2016}}</ref> |
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<ref name="zsh echo">{{Cite web|url=http://zsh.sourceforge.net/Doc/Release/Shell-Builtin-Commands.html|title=zsh: 17 Shell Builtin Commands|website=zsh.sourceforge.net}}</ref> |
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<ref name="man echo">{{cite web|title=8th Edition Unix echo man page|url=http://man.cat-v.org/unix_8th/1/echo|access-date=24 July 2016}}</ref> |
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<ref name="Bash-Builtins">{{Cite web|url=https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html|title=Bash Builtins (Bash Reference Manual)|website=www.gnu.org}}</ref> |
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<ref name="echo limitations">{{cite web|title=Autoconf documentation on echo portability|url=https://www.gnu.org/software/autoconf/manual/autoconf-2.66/html_node/Limitations-of-Builtins.html#echo|publisher=Free Software Foundation|access-date=24 July 2016}}</ref> |
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<ref name="RUNNINGMSDOS">{{Cite book|author-last=Wolverton|author-first=Van|title=Running MS-DOS Version 6.22 (20th Anniversary Edition), 6th Revised edition|date=2003|publisher=[[Microsoft Press]]|isbn=0-7356-1812-7}}</ref> |
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<ref name="jatomes">[http://www.jatomes.com/Help/Os2Bat.php#ECHO]{{dead link|date=September 2020}}</ref> |
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<ref name="flexos user guide">[http://www.bitsavers.org/pdf/digitalResearch/flexos/1073-2003_FlexOS_Users_Guide_V1.3_Nov86.pdf]{{dead link|date=September 2020}}</ref> |
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<ref name="tripos">{{cite web |url=https://www.pagetable.com/docs/amigados_tripos/tripos_manuals.pdf |title= Manual |website=www.pagetable.com|access-date=2020-09-12}}</ref> |
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<ref name="z80 user guide">[https://www.z80cpu.eu/mirrors/oldcomputers.dyndns.org/public/pub/rechner/zilog/zds/z80-rio_os_userman.pdf Z80-RIO OPERATING SYSTEM USER'S MANUAL]</ref> |
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<ref name="os-9 guru">{{cite book|author=Paul S. Dayan|year=1992|title=The OS-9 Guru - 1 : The Facts|publisher=Galactic Industrial Limited|isbn=0-9519228-0-7}}</ref> |
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<ref name="reader">{{cite techreport |first1=M. D. |last1=McIlroy |author-link1=Doug McIlroy |year=1987 |url=http://www.cs.dartmouth.edu/~doug/reader.pdf |title=A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 |series=CSTR |number=139 |institution=Bell Labs}}</ref> |
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<ref name="rugheimer-spanik-amigados">{{Cite web|url=http://archive.org/details/1988-rugheimer-spanik-amigados-quick-reference|title=AmigaDOS quick reference|first1=Hannes|last1=Rügheimer|first2=Christian|last2=Spanik|date=September 12, 1988|publisher=Grand Rapids, Mi : Abacus|via=Internet Archive}}</ref> |
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<ref name="computinghistory">{{Cite web|url=http://chrisacorns.computinghistory.org.uk/Panos.html#CL|title=Chris's Acorns: Panos|website=chrisacorns.computinghistory.org.uk}}</ref> |
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<ref name="windows-commands">{{Cite web|url=https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/echo|title=echo|website=docs.microsoft.com}}</ref> |
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<ref name="flexusergroup">{{Cite web|url=http://www.flexusergroup.com/flexusergroup/pdfs/swflexum.pdf|title=FLEX 9.0 User's Manual}}</ref> |
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<ref name="teamnaconsulting">[http://www.teamnaconsulting.com/compresources/pdfs/c01687363.pdf MPE/iX Command Reference Manual]</ref> |
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<ref name="reactos">{{Cite web|url=https://github.com/reactos/reactos|title=reactos/reactos|website=GitHub}}</ref> |
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<ref name="kolibrios">{{Cite web|url=http://wiki.kolibrios.org/wiki/Shell|title=Shell - KolibriOS wiki|website=wiki.kolibrios.org}}</ref> |
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<ref name="multics">{{Cite web|url=https://www.multicians.org/multics-commands.html|title=Multics Commands|website=www.multicians.org}}</ref> |
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}} |
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==Further reading== |
==Further reading== |
Revision as of 07:20, 17 October 2021
Original author(s) | Douglas McIlroy (AT&T Bell Laboratories) |
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Developer(s) | Various open-source and commercial developers |
Operating system | Multics, Unix, Unix-like, V, Plan 9, Inferno, FLEX, TRIPOS, AmigaDOS, Z80-RIO, OS-9, DOS, MSX-DOS, Panos, FlexOS, SISNE plus, OS/2, Windows, ReactOS, MPE/iX, KolibriOS, SymbOS |
Platform | Cross-platform |
Type | Command |
In computing, echo
is a command that outputs the strings that are passed to it as arguments. It is a command available in various operating system shells and typically used in shell scripts and batch files to output status text to the screen[1] or a computer file, or as a source part of a pipeline.
Implementations
The command is available in the following operating systems:
- Multics[2]
- TSC FLEX[3]
- MetaComCo TRIPOS[4]
- Zilog Z80-RIO[5]
- Microware OS-9[6]
- DOS
- Acorn Computers Panos[7]
- Digital Research FlexOS[8]
- IBM OS/2[9]
- Microsoft Windows[10]
- ReactOS[11]
- HP MPE/iX[12]
- KolibriOS[13]
- SymbOS
- Unix and Unix-like operating systems
Many shells, including all Bourne-like (such as Bash[14] or zsh[15]) and Csh-like shells as well as COMMAND.COM and cmd.exe implement echo
as a builtin command.
The command is also available in the EFI shell.[16]
History
echo
began within Multics. After it was programmed in C by Doug McIlroy as a "finger exercise" and proved to be useful, it became part of Version 2 Unix. echo -n
in Version 7 replaced prompt
, (which behaved like echo
but without terminating its output with a line delimiter).[17]
On PWB/UNIX and later Unix System III, echo
started expanding C escape sequences such as \n
with the notable difference that octal escape sequences were expressed as \0ooo
instead of \ooo
in C.[18]
Eighth Edition Unix echo
only did the escape expansion when passed a -e
option,[19] and that behaviour was copied by a few other implementations such as the builtin echo
command of Bash or zsh and GNU echo
.
On MS-DOS, the command is available in versions 2 and later.[20]
Nowadays, several incompatible implementations of echo
exist on different operating systems (often several on the same system), some of them expanding escape sequences by default, some of them not, some of them accepting options (the list of which varying with implementations), some of them not.
The POSIX Specification of echo
[21] leaves the behaviour unspecified if the first argument is -n
or any argument contain backslash characters while the Unix specification (XSI option in POSIX) mandates the expansion of (some) sequences and does not allow any option processing. In practice, many echo
implementations are not compliant in the default environment.
Because of these variations in behaviour, echo
is considered a non-portable command on Unix-like systems[22] and the printf
command (where available, introduced by Ninth Edition Unix) is preferred instead.
Usage examples
C:\>echo Hello world
Hello world
Using ANSI escape code SGR sequences, compatible terminals can print out colored text.
Using a UNIX System III-style implementation:
BGRED=`echo "\033[41m"`
FGBLUE=`echo "\033[35m"`
BGGREEN=`echo "\033[42m"`
NORMAL=`echo "\033[m"`
Or a Unix Version 8-style implementation (such as Bash when not in Unix-conformance mode):
BGRED=`echo -e "\033[41m"`
FGBLUE=`echo -e "\033[35m"`
BGGREEN=`echo -e "\033[42m"`
NORMAL=`echo -e "\033[m"`
and after:
echo "${FGBLUE} Text in blue ${NORMAL}"
echo "Text normal"
echo "${BGRED} Background in red"
echo "${BGGREEN} Background in Green and back to Normal ${NORMAL}"
Portably with printf
:
BGRED=`printf '\33[41m'`
NORMAL=`printf '\33[m'`
printf '%s\n' "${BGRED}Text on red background${NORMAL}"
See also
References
- ^ Rügheimer, Hannes; Spanik, Christian (September 12, 1988). "AmigaDOS quick reference". Grand Rapids, Mi : Abacus – via Internet Archive.
- ^ "Multics Commands". www.multicians.org.
- ^ "FLEX 9.0 User's Manual" (PDF).
- ^ "Manual" (PDF). www.pagetable.com. Retrieved 2020-09-12.
- ^ Z80-RIO OPERATING SYSTEM USER'S MANUAL
- ^ Paul S. Dayan (1992). The OS-9 Guru - 1 : The Facts. Galactic Industrial Limited. ISBN 0-9519228-0-7.
- ^ "Chris's Acorns: Panos". chrisacorns.computinghistory.org.uk.
- ^ [1][dead link]
- ^ [2][dead link]
- ^ "echo". docs.microsoft.com.
- ^ "reactos/reactos". GitHub.
- ^ MPE/iX Command Reference Manual
- ^ "Shell - KolibriOS wiki". wiki.kolibrios.org.
- ^ "Bash Builtins (Bash Reference Manual)". www.gnu.org.
- ^ "zsh: 17 Shell Builtin Commands". zsh.sourceforge.net.
- ^ "EFI Shells and Scripting". Intel. Retrieved 2013-09-25.
- ^ McIlroy, M. D. (1987). A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 (PDF) (Technical report). CSTR. Bell Labs. 139.
- ^ Mascheck, Sven. "echo and printf behaviour". Retrieved 24 July 2016.
- ^ "8th Edition Unix echo man page". Retrieved 24 July 2016.
- ^ Wolverton, Van (2003). Running MS-DOS Version 6.22 (20th Anniversary Edition), 6th Revised edition. Microsoft Press. ISBN 0-7356-1812-7.
- ^ The Single UNIX Specification, Version 4 from The Open Group : write arguments to standard output – Shell and Utilities Reference,
- ^ "Autoconf documentation on echo portability". Free Software Foundation. Retrieved 24 July 2016.
Further reading
- Wolverton, Van (1990). MS-DOS Commands: Microsoft Quick Reference, 4th Revised edition. Microsoft Press. ISBN 978-1556152894.
- Kathy Ivens; Brian Proffit (1993). OS/2 Inside & Out. Osborne McGraw-Hill. ISBN 978-0078818714.
- Frisch, Æleen (2001). Windows 2000 Commands Pocket Reference. O'Reilly. ISBN 978-0-596-00148-3.
External links
- The Single UNIX Specification, Version 4 from The Open Group : write arguments to standard output – Shell and Utilities Reference,
- Plan 9 Programmer's Manual, Volume 1 –
- Inferno General commands Manual –
- Microsoft TechNet Echo article