What is the difference between the commands builtin cd and cd?
Clash Royale CLAN TAG#URR8PPP
I encountered a Linux command, builtin cd
.
What is the difference between the commands builtin cd
and cd
?
In fact, I made some researches about the difference, but I could not find a remarkable and significant explanation about this.
bash shell cd-command
add a comment |
I encountered a Linux command, builtin cd
.
What is the difference between the commands builtin cd
and cd
?
In fact, I made some researches about the difference, but I could not find a remarkable and significant explanation about this.
bash shell cd-command
1
See also unix.stackexchange.com/q/38808/117549
– Jeff Schaller
Jan 19 at 10:49
See also: stackoverflow.com/q/15691977/974555
– gerrit
Jan 19 at 17:45
add a comment |
I encountered a Linux command, builtin cd
.
What is the difference between the commands builtin cd
and cd
?
In fact, I made some researches about the difference, but I could not find a remarkable and significant explanation about this.
bash shell cd-command
I encountered a Linux command, builtin cd
.
What is the difference between the commands builtin cd
and cd
?
In fact, I made some researches about the difference, but I could not find a remarkable and significant explanation about this.
bash shell cd-command
bash shell cd-command
edited Jan 19 at 12:26
Peter Mortensen
90158
90158
asked Jan 19 at 9:31
GoktugGoktug
33111
33111
1
See also unix.stackexchange.com/q/38808/117549
– Jeff Schaller
Jan 19 at 10:49
See also: stackoverflow.com/q/15691977/974555
– gerrit
Jan 19 at 17:45
add a comment |
1
See also unix.stackexchange.com/q/38808/117549
– Jeff Schaller
Jan 19 at 10:49
See also: stackoverflow.com/q/15691977/974555
– gerrit
Jan 19 at 17:45
1
1
See also unix.stackexchange.com/q/38808/117549
– Jeff Schaller
Jan 19 at 10:49
See also unix.stackexchange.com/q/38808/117549
– Jeff Schaller
Jan 19 at 10:49
See also: stackoverflow.com/q/15691977/974555
– gerrit
Jan 19 at 17:45
See also: stackoverflow.com/q/15691977/974555
– gerrit
Jan 19 at 17:45
add a comment |
2 Answers
2
active
oldest
votes
The cd
command is a built-in, so normally builtin cd
will do the same thing as cd
. But there is a difference if cd
is redefined as a function or alias, in which case cd
will call the function/alias but builtin cd
will still change the directory (in other words, will keep the built-in accessible even if clobbered by a function.)
For example:
user:~$ cd () echo "I won't let you change directories";
user:~$ cd mysubdir
I won't let you change directories
user:~$ builtin cd mysubdir
user:~/mysubdir$ unset -f cd # undefine function
Or with an alias:
user:~$ alias cd='echo Trying to cd to'
user:~$ cd mysubdir
Trying to cd to mysubdir
user:~$ builtin cd mysubdir
user:~/mysubdir$ unalias cd # undefine alias
Using builtin
is also a good way to define a cd
function that does something and changes directory (since calling cd
from it would just keep calling the function again in an endless recursion.)
For example:
user:~ $ cd () echo "Changing directory to $1-home"; builtin cd "$@";
user:~ $ cd mysubdir
Changing directory to mysubdir
user:~/mysubdir $ cd
Changing directory to home
user:~ $ unset -f cd # undefine function
5
+1 The examples are particularly illustrative here.
– Tashus
Jan 19 at 16:09
2
In the case of an alias, is there any difference betweenbuiltin cd mysubdir
andcd mysubdir
?
– gerrit
Jan 19 at 17:46
2
@gerrit Only if there is a function namedcd
, in which casecd
would bypass the alias and run the function. See stackoverflow.com/a/16506263/4518341
– wjandrea
Jan 19 at 22:08
add a comment |
In most instances, there is no difference (but see below). The cd
command is a built-in command in all shells. It needs to be built-in1 as an external command can not change the environment of the invoking shell, and changing the working directory constitutes a change in its environment.
The bash
command builtin
forces the shell to use the built-in version of a command, even though there may be a shell function, alias, or external command available with the same name.
In the case where there is e.g. a shell function with the name cd
, then builtin cd
would not call that. Using builtin cd
bypasses any overloaded functionality that may have been added through a shell function or alias by the user.
Example:
The cd
built-in command may be overloaded by a function that updates the prompt:
cd()
builtin cd "$@" && PS1=$(__update_prompt)
where __update_prompt
is some other user-supplied function that outputs a string.
The builtin cd
in the function would not call the function recursively. Using builtin cd
in a shell where this function is active, would additionally not call the function.
1There are Unices with an external cd
command (macOS, and, I believe, Solaris). The purpose of that command, which can't change the working directory for a shell, is possibly to satisfy the POSIX standard, which lists cd
as one of the external utilities that should be available (cd
is not one of the "special builtin utilities"). It may also serve as a test to see whether changing work directory to a given directory would be possible.
FWIW, MacOS would also fall in the category of OSs with an externalcd
command.
– yoann
Jan 19 at 10:40
@yoann Indeed it does.
– Kusalananda
Jan 19 at 10:42
Thank you - you've made my day with top notch, well researched,, footnoted pedantry.
– james
Jan 19 at 18:27
most shells -- it's an external program for execlineb, but then it's cd will then exec its remaining arguments
– Grump
Jan 20 at 9:37
add a comment |
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2 Answers
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2 Answers
2
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oldest
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The cd
command is a built-in, so normally builtin cd
will do the same thing as cd
. But there is a difference if cd
is redefined as a function or alias, in which case cd
will call the function/alias but builtin cd
will still change the directory (in other words, will keep the built-in accessible even if clobbered by a function.)
For example:
user:~$ cd () echo "I won't let you change directories";
user:~$ cd mysubdir
I won't let you change directories
user:~$ builtin cd mysubdir
user:~/mysubdir$ unset -f cd # undefine function
Or with an alias:
user:~$ alias cd='echo Trying to cd to'
user:~$ cd mysubdir
Trying to cd to mysubdir
user:~$ builtin cd mysubdir
user:~/mysubdir$ unalias cd # undefine alias
Using builtin
is also a good way to define a cd
function that does something and changes directory (since calling cd
from it would just keep calling the function again in an endless recursion.)
For example:
user:~ $ cd () echo "Changing directory to $1-home"; builtin cd "$@";
user:~ $ cd mysubdir
Changing directory to mysubdir
user:~/mysubdir $ cd
Changing directory to home
user:~ $ unset -f cd # undefine function
5
+1 The examples are particularly illustrative here.
– Tashus
Jan 19 at 16:09
2
In the case of an alias, is there any difference betweenbuiltin cd mysubdir
andcd mysubdir
?
– gerrit
Jan 19 at 17:46
2
@gerrit Only if there is a function namedcd
, in which casecd
would bypass the alias and run the function. See stackoverflow.com/a/16506263/4518341
– wjandrea
Jan 19 at 22:08
add a comment |
The cd
command is a built-in, so normally builtin cd
will do the same thing as cd
. But there is a difference if cd
is redefined as a function or alias, in which case cd
will call the function/alias but builtin cd
will still change the directory (in other words, will keep the built-in accessible even if clobbered by a function.)
For example:
user:~$ cd () echo "I won't let you change directories";
user:~$ cd mysubdir
I won't let you change directories
user:~$ builtin cd mysubdir
user:~/mysubdir$ unset -f cd # undefine function
Or with an alias:
user:~$ alias cd='echo Trying to cd to'
user:~$ cd mysubdir
Trying to cd to mysubdir
user:~$ builtin cd mysubdir
user:~/mysubdir$ unalias cd # undefine alias
Using builtin
is also a good way to define a cd
function that does something and changes directory (since calling cd
from it would just keep calling the function again in an endless recursion.)
For example:
user:~ $ cd () echo "Changing directory to $1-home"; builtin cd "$@";
user:~ $ cd mysubdir
Changing directory to mysubdir
user:~/mysubdir $ cd
Changing directory to home
user:~ $ unset -f cd # undefine function
5
+1 The examples are particularly illustrative here.
– Tashus
Jan 19 at 16:09
2
In the case of an alias, is there any difference betweenbuiltin cd mysubdir
andcd mysubdir
?
– gerrit
Jan 19 at 17:46
2
@gerrit Only if there is a function namedcd
, in which casecd
would bypass the alias and run the function. See stackoverflow.com/a/16506263/4518341
– wjandrea
Jan 19 at 22:08
add a comment |
The cd
command is a built-in, so normally builtin cd
will do the same thing as cd
. But there is a difference if cd
is redefined as a function or alias, in which case cd
will call the function/alias but builtin cd
will still change the directory (in other words, will keep the built-in accessible even if clobbered by a function.)
For example:
user:~$ cd () echo "I won't let you change directories";
user:~$ cd mysubdir
I won't let you change directories
user:~$ builtin cd mysubdir
user:~/mysubdir$ unset -f cd # undefine function
Or with an alias:
user:~$ alias cd='echo Trying to cd to'
user:~$ cd mysubdir
Trying to cd to mysubdir
user:~$ builtin cd mysubdir
user:~/mysubdir$ unalias cd # undefine alias
Using builtin
is also a good way to define a cd
function that does something and changes directory (since calling cd
from it would just keep calling the function again in an endless recursion.)
For example:
user:~ $ cd () echo "Changing directory to $1-home"; builtin cd "$@";
user:~ $ cd mysubdir
Changing directory to mysubdir
user:~/mysubdir $ cd
Changing directory to home
user:~ $ unset -f cd # undefine function
The cd
command is a built-in, so normally builtin cd
will do the same thing as cd
. But there is a difference if cd
is redefined as a function or alias, in which case cd
will call the function/alias but builtin cd
will still change the directory (in other words, will keep the built-in accessible even if clobbered by a function.)
For example:
user:~$ cd () echo "I won't let you change directories";
user:~$ cd mysubdir
I won't let you change directories
user:~$ builtin cd mysubdir
user:~/mysubdir$ unset -f cd # undefine function
Or with an alias:
user:~$ alias cd='echo Trying to cd to'
user:~$ cd mysubdir
Trying to cd to mysubdir
user:~$ builtin cd mysubdir
user:~/mysubdir$ unalias cd # undefine alias
Using builtin
is also a good way to define a cd
function that does something and changes directory (since calling cd
from it would just keep calling the function again in an endless recursion.)
For example:
user:~ $ cd () echo "Changing directory to $1-home"; builtin cd "$@";
user:~ $ cd mysubdir
Changing directory to mysubdir
user:~/mysubdir $ cd
Changing directory to home
user:~ $ unset -f cd # undefine function
edited Jan 20 at 1:37
answered Jan 19 at 9:50
filbrandenfilbranden
8,09621139
8,09621139
5
+1 The examples are particularly illustrative here.
– Tashus
Jan 19 at 16:09
2
In the case of an alias, is there any difference betweenbuiltin cd mysubdir
andcd mysubdir
?
– gerrit
Jan 19 at 17:46
2
@gerrit Only if there is a function namedcd
, in which casecd
would bypass the alias and run the function. See stackoverflow.com/a/16506263/4518341
– wjandrea
Jan 19 at 22:08
add a comment |
5
+1 The examples are particularly illustrative here.
– Tashus
Jan 19 at 16:09
2
In the case of an alias, is there any difference betweenbuiltin cd mysubdir
andcd mysubdir
?
– gerrit
Jan 19 at 17:46
2
@gerrit Only if there is a function namedcd
, in which casecd
would bypass the alias and run the function. See stackoverflow.com/a/16506263/4518341
– wjandrea
Jan 19 at 22:08
5
5
+1 The examples are particularly illustrative here.
– Tashus
Jan 19 at 16:09
+1 The examples are particularly illustrative here.
– Tashus
Jan 19 at 16:09
2
2
In the case of an alias, is there any difference between
builtin cd mysubdir
and cd mysubdir
?– gerrit
Jan 19 at 17:46
In the case of an alias, is there any difference between
builtin cd mysubdir
and cd mysubdir
?– gerrit
Jan 19 at 17:46
2
2
@gerrit Only if there is a function named
cd
, in which case cd
would bypass the alias and run the function. See stackoverflow.com/a/16506263/4518341– wjandrea
Jan 19 at 22:08
@gerrit Only if there is a function named
cd
, in which case cd
would bypass the alias and run the function. See stackoverflow.com/a/16506263/4518341– wjandrea
Jan 19 at 22:08
add a comment |
In most instances, there is no difference (but see below). The cd
command is a built-in command in all shells. It needs to be built-in1 as an external command can not change the environment of the invoking shell, and changing the working directory constitutes a change in its environment.
The bash
command builtin
forces the shell to use the built-in version of a command, even though there may be a shell function, alias, or external command available with the same name.
In the case where there is e.g. a shell function with the name cd
, then builtin cd
would not call that. Using builtin cd
bypasses any overloaded functionality that may have been added through a shell function or alias by the user.
Example:
The cd
built-in command may be overloaded by a function that updates the prompt:
cd()
builtin cd "$@" && PS1=$(__update_prompt)
where __update_prompt
is some other user-supplied function that outputs a string.
The builtin cd
in the function would not call the function recursively. Using builtin cd
in a shell where this function is active, would additionally not call the function.
1There are Unices with an external cd
command (macOS, and, I believe, Solaris). The purpose of that command, which can't change the working directory for a shell, is possibly to satisfy the POSIX standard, which lists cd
as one of the external utilities that should be available (cd
is not one of the "special builtin utilities"). It may also serve as a test to see whether changing work directory to a given directory would be possible.
FWIW, MacOS would also fall in the category of OSs with an externalcd
command.
– yoann
Jan 19 at 10:40
@yoann Indeed it does.
– Kusalananda
Jan 19 at 10:42
Thank you - you've made my day with top notch, well researched,, footnoted pedantry.
– james
Jan 19 at 18:27
most shells -- it's an external program for execlineb, but then it's cd will then exec its remaining arguments
– Grump
Jan 20 at 9:37
add a comment |
In most instances, there is no difference (but see below). The cd
command is a built-in command in all shells. It needs to be built-in1 as an external command can not change the environment of the invoking shell, and changing the working directory constitutes a change in its environment.
The bash
command builtin
forces the shell to use the built-in version of a command, even though there may be a shell function, alias, or external command available with the same name.
In the case where there is e.g. a shell function with the name cd
, then builtin cd
would not call that. Using builtin cd
bypasses any overloaded functionality that may have been added through a shell function or alias by the user.
Example:
The cd
built-in command may be overloaded by a function that updates the prompt:
cd()
builtin cd "$@" && PS1=$(__update_prompt)
where __update_prompt
is some other user-supplied function that outputs a string.
The builtin cd
in the function would not call the function recursively. Using builtin cd
in a shell where this function is active, would additionally not call the function.
1There are Unices with an external cd
command (macOS, and, I believe, Solaris). The purpose of that command, which can't change the working directory for a shell, is possibly to satisfy the POSIX standard, which lists cd
as one of the external utilities that should be available (cd
is not one of the "special builtin utilities"). It may also serve as a test to see whether changing work directory to a given directory would be possible.
FWIW, MacOS would also fall in the category of OSs with an externalcd
command.
– yoann
Jan 19 at 10:40
@yoann Indeed it does.
– Kusalananda
Jan 19 at 10:42
Thank you - you've made my day with top notch, well researched,, footnoted pedantry.
– james
Jan 19 at 18:27
most shells -- it's an external program for execlineb, but then it's cd will then exec its remaining arguments
– Grump
Jan 20 at 9:37
add a comment |
In most instances, there is no difference (but see below). The cd
command is a built-in command in all shells. It needs to be built-in1 as an external command can not change the environment of the invoking shell, and changing the working directory constitutes a change in its environment.
The bash
command builtin
forces the shell to use the built-in version of a command, even though there may be a shell function, alias, or external command available with the same name.
In the case where there is e.g. a shell function with the name cd
, then builtin cd
would not call that. Using builtin cd
bypasses any overloaded functionality that may have been added through a shell function or alias by the user.
Example:
The cd
built-in command may be overloaded by a function that updates the prompt:
cd()
builtin cd "$@" && PS1=$(__update_prompt)
where __update_prompt
is some other user-supplied function that outputs a string.
The builtin cd
in the function would not call the function recursively. Using builtin cd
in a shell where this function is active, would additionally not call the function.
1There are Unices with an external cd
command (macOS, and, I believe, Solaris). The purpose of that command, which can't change the working directory for a shell, is possibly to satisfy the POSIX standard, which lists cd
as one of the external utilities that should be available (cd
is not one of the "special builtin utilities"). It may also serve as a test to see whether changing work directory to a given directory would be possible.
In most instances, there is no difference (but see below). The cd
command is a built-in command in all shells. It needs to be built-in1 as an external command can not change the environment of the invoking shell, and changing the working directory constitutes a change in its environment.
The bash
command builtin
forces the shell to use the built-in version of a command, even though there may be a shell function, alias, or external command available with the same name.
In the case where there is e.g. a shell function with the name cd
, then builtin cd
would not call that. Using builtin cd
bypasses any overloaded functionality that may have been added through a shell function or alias by the user.
Example:
The cd
built-in command may be overloaded by a function that updates the prompt:
cd()
builtin cd "$@" && PS1=$(__update_prompt)
where __update_prompt
is some other user-supplied function that outputs a string.
The builtin cd
in the function would not call the function recursively. Using builtin cd
in a shell where this function is active, would additionally not call the function.
1There are Unices with an external cd
command (macOS, and, I believe, Solaris). The purpose of that command, which can't change the working directory for a shell, is possibly to satisfy the POSIX standard, which lists cd
as one of the external utilities that should be available (cd
is not one of the "special builtin utilities"). It may also serve as a test to see whether changing work directory to a given directory would be possible.
edited Jan 19 at 12:31
answered Jan 19 at 9:39
KusalanandaKusalananda
128k16241398
128k16241398
FWIW, MacOS would also fall in the category of OSs with an externalcd
command.
– yoann
Jan 19 at 10:40
@yoann Indeed it does.
– Kusalananda
Jan 19 at 10:42
Thank you - you've made my day with top notch, well researched,, footnoted pedantry.
– james
Jan 19 at 18:27
most shells -- it's an external program for execlineb, but then it's cd will then exec its remaining arguments
– Grump
Jan 20 at 9:37
add a comment |
FWIW, MacOS would also fall in the category of OSs with an externalcd
command.
– yoann
Jan 19 at 10:40
@yoann Indeed it does.
– Kusalananda
Jan 19 at 10:42
Thank you - you've made my day with top notch, well researched,, footnoted pedantry.
– james
Jan 19 at 18:27
most shells -- it's an external program for execlineb, but then it's cd will then exec its remaining arguments
– Grump
Jan 20 at 9:37
FWIW, MacOS would also fall in the category of OSs with an external
cd
command.– yoann
Jan 19 at 10:40
FWIW, MacOS would also fall in the category of OSs with an external
cd
command.– yoann
Jan 19 at 10:40
@yoann Indeed it does.
– Kusalananda
Jan 19 at 10:42
@yoann Indeed it does.
– Kusalananda
Jan 19 at 10:42
Thank you - you've made my day with top notch, well researched,, footnoted pedantry.
– james
Jan 19 at 18:27
Thank you - you've made my day with top notch, well researched,, footnoted pedantry.
– james
Jan 19 at 18:27
most shells -- it's an external program for execlineb, but then it's cd will then exec its remaining arguments
– Grump
Jan 20 at 9:37
most shells -- it's an external program for execlineb, but then it's cd will then exec its remaining arguments
– Grump
Jan 20 at 9:37
add a comment |
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1
See also unix.stackexchange.com/q/38808/117549
– Jeff Schaller
Jan 19 at 10:49
See also: stackoverflow.com/q/15691977/974555
– gerrit
Jan 19 at 17:45