Clash Royale CLAN TAG#URR8PPP

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We have env(1) to modify the environment of the command we want to run (for example env MANPAGER=more man dtrace). Is there something similar but for modifying the directory that the command is going to be started in?

Ideally, I would like it to look like this:

theMagicCommand /new/cwd myProgram

This way it could be "chained" with other env(1)-like commands, e.g.,

daemon -p /tmp/pid env VAR=value theMagicCommand /new/cwd myProgram

So far I can think of the following solution, which unfortunately do not have the same interface as env(1):

cd /new/cwd && myProgram

Also, I can just create a simple shell script like this:

#! /bin/sh -
cd "$1:?Missing the new working directory" || exit 1
shift
exec "$@:?Missing the command to run"

but I am looking for something that already exists (at least on macOS and FreeBSD).

myProgram is not necessarily a desktop application (in which case I could just use the Path key in a .desktop file).

edited 43 mins ago

asked 1 hour ago

Mateusz Piotrowski

1,78421537

add a comment |

up vote
4
down vote

favorite

Ideally, I would like it to look like this:

theMagicCommand /new/cwd myProgram

This way it could be "chained" with other env(1)-like commands, e.g.,

daemon -p /tmp/pid env VAR=value theMagicCommand /new/cwd myProgram

So far I can think of the following solution, which unfortunately do not have the same interface as env(1):

cd /new/cwd && myProgram

Also, I can just create a simple shell script like this:

#! /bin/sh -
cd "$1:?Missing the new working directory" || exit 1
shift
exec "$@:?Missing the command to run"

but I am looking for something that already exists (at least on macOS and FreeBSD).

myProgram is not necessarily a desktop application (in which case I could just use the Path key in a .desktop file).

edited 43 mins ago

asked 1 hour ago

Mateusz Piotrowski

1,78421537

add a comment |

up vote
4
down vote

favorite

Ideally, I would like it to look like this:

theMagicCommand /new/cwd myProgram

This way it could be "chained" with other env(1)-like commands, e.g.,

daemon -p /tmp/pid env VAR=value theMagicCommand /new/cwd myProgram

So far I can think of the following solution, which unfortunately do not have the same interface as env(1):

cd /new/cwd && myProgram

Also, I can just create a simple shell script like this:

#! /bin/sh -
cd "$1:?Missing the new working directory" || exit 1
shift
exec "$@:?Missing the command to run"

but I am looking for something that already exists (at least on macOS and FreeBSD).

myProgram is not necessarily a desktop application (in which case I could just use the Path key in a .desktop file).

edited 43 mins ago

asked 1 hour ago

Mateusz Piotrowski

1,78421537

Ideally, I would like it to look like this:

theMagicCommand /new/cwd myProgram

This way it could be "chained" with other env(1)-like commands, e.g.,

daemon -p /tmp/pid env VAR=value theMagicCommand /new/cwd myProgram

So far I can think of the following solution, which unfortunately do not have the same interface as env(1):

cd /new/cwd && myProgram

Also, I can just create a simple shell script like this:

#! /bin/sh -
cd "$1:?Missing the new working directory" || exit 1
shift
exec "$@:?Missing the command to run"

but I am looking for something that already exists (at least on macOS and FreeBSD).

myProgram is not necessarily a desktop application (in which case I could just use the Path key in a .desktop file).

shell freebsd cwd

edited 43 mins ago

asked 1 hour ago

Mateusz Piotrowski

1,78421537

edited 43 mins ago

asked 1 hour ago

Mateusz Piotrowski

1,78421537

edited 43 mins ago

asked 1 hour ago

Mateusz Piotrowski

1,78421537

asked 1 hour ago

Mateusz Piotrowski

1,78421537

asked 1 hour ago

Mateusz Piotrowski

1,78421537

add a comment |

3 Answers
3

active

oldest

votes

up vote
4
down vote

AFAIK, there is no such dedicated utility in the POSIX tool chest. But it's common to invoke sh to set up an environment (cwd, limits, stdout/in/err, umask...) before running a command as you do in your sh script.

But you don't have to write that script in a file, you can just inline it:

sh -c 'CDPATH= cd -P -- "$1" && shift && exec "$@"' sh /some/dir cmd args

(assuming the directory is not -). Adding CDPATH= (in case there's one in the environment) and -P for it to behave more like a straight chdir().

Alternatively, you could use perl whose chdir() does a straight chdir() out of the box.

perl -e 'chdir(shift@ARGV) or die "chdir: $!"; exec @ARGV or die "exec: $!"
 ' /some/dir cmd args

edited 1 hour ago

answered 1 hour ago

Stéphane Chazelas

292k54544884

Oh, yeah. This is indded a very handy variation of the script I included in my question. I was afraid that the utility I am looking for does not exist since its functionality is already available with a relatively short sh(1) oneliner.
– Mateusz Piotrowski
1 hour ago

add a comment |

up vote
1
down vote

You could use a subshell:

$ pwd
/home/user
$ (cd /bin && pwd)
/bin
$ pwd
/home/user

A possible downside of this approach is that the values of the variables are not preserved in the parent shell, but it may be useful in certain cases:

$ var=foo; echo "$var"
foo
$ (var=bar; echo "$var")
bar
$ echo "$var"
foo

answered 53 mins ago

nxnev

2,5482423

A subshell is not a solution. It is not a utility and unfortunately it cannot be chained the way you can chain env(1)-like variables.
– Mateusz Piotrowski
42 mins ago

@MateuszPiotrowski Would this approach be valid if you put the entire chain of commands within the subshell? If I understand correctly, it will be basically the same as having a separate script or explicitly calling another interpreter, at least in a shell context.
– nxnev
32 mins ago

In a way, yes. In order to use a subshell we have to be in a shell of some sort. In case you'd like to feed this command to execve you'd have to wrap your subshell in sh -c anyway.
– Mateusz Piotrowski
21 mins ago

add a comment |

up vote
0
down vote

The toolsets used in the daemontools world, and elsewhere, have this and more besides; have had for many years; and are widely available.

Wayne Marshall's perp has runtool:
```
runtool -c /new/cwd myProgram
```

Laurent Bercot's execline has cd:
```
cd /new/cwd myProgram
```

my nosh toolset has chdir:
```
chdir /new/cwd myProgram
```

All of these are chain-loading tools, designed to be used in exactly these sorts of chains. There is a wide selection of chain-loading tools in these toolkits for other purposes.

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3 Answers
3

active

oldest

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3 Answers
3

active

oldest

votes

up vote
4
down vote

But you don't have to write that script in a file, you can just inline it:

sh -c 'CDPATH= cd -P -- "$1" && shift && exec "$@"' sh /some/dir cmd args

(assuming the directory is not -). Adding CDPATH= (in case there's one in the environment) and -P for it to behave more like a straight chdir().

Alternatively, you could use perl whose chdir() does a straight chdir() out of the box.

perl -e 'chdir(shift@ARGV) or die "chdir: $!"; exec @ARGV or die "exec: $!"
 ' /some/dir cmd args

edited 1 hour ago

answered 1 hour ago

Stéphane Chazelas

292k54544884

Oh, yeah. This is indded a very handy variation of the script I included in my question. I was afraid that the utility I am looking for does not exist since its functionality is already available with a relatively short sh(1) oneliner.
– Mateusz Piotrowski
1 hour ago

add a comment |

up vote
4
down vote

But you don't have to write that script in a file, you can just inline it:

sh -c 'CDPATH= cd -P -- "$1" && shift && exec "$@"' sh /some/dir cmd args

(assuming the directory is not -). Adding CDPATH= (in case there's one in the environment) and -P for it to behave more like a straight chdir().

Alternatively, you could use perl whose chdir() does a straight chdir() out of the box.

perl -e 'chdir(shift@ARGV) or die "chdir: $!"; exec @ARGV or die "exec: $!"
 ' /some/dir cmd args

edited 1 hour ago

answered 1 hour ago

Stéphane Chazelas

292k54544884

Oh, yeah. This is indded a very handy variation of the script I included in my question. I was afraid that the utility I am looking for does not exist since its functionality is already available with a relatively short sh(1) oneliner.
– Mateusz Piotrowski
1 hour ago

add a comment |

up vote
4
down vote

But you don't have to write that script in a file, you can just inline it:

sh -c 'CDPATH= cd -P -- "$1" && shift && exec "$@"' sh /some/dir cmd args

(assuming the directory is not -). Adding CDPATH= (in case there's one in the environment) and -P for it to behave more like a straight chdir().

Alternatively, you could use perl whose chdir() does a straight chdir() out of the box.

perl -e 'chdir(shift@ARGV) or die "chdir: $!"; exec @ARGV or die "exec: $!"
 ' /some/dir cmd args

edited 1 hour ago

answered 1 hour ago

Stéphane Chazelas

292k54544884

But you don't have to write that script in a file, you can just inline it:

sh -c 'CDPATH= cd -P -- "$1" && shift && exec "$@"' sh /some/dir cmd args

(assuming the directory is not -). Adding CDPATH= (in case there's one in the environment) and -P for it to behave more like a straight chdir().

Alternatively, you could use perl whose chdir() does a straight chdir() out of the box.

perl -e 'chdir(shift@ARGV) or die "chdir: $!"; exec @ARGV or die "exec: $!"
 ' /some/dir cmd args

edited 1 hour ago

answered 1 hour ago

Stéphane Chazelas

292k54544884

edited 1 hour ago

answered 1 hour ago

Stéphane Chazelas

292k54544884

answered 1 hour ago

Stéphane Chazelas

292k54544884

answered 1 hour ago

Stéphane Chazelas

292k54544884

Oh, yeah. This is indded a very handy variation of the script I included in my question. I was afraid that the utility I am looking for does not exist since its functionality is already available with a relatively short sh(1) oneliner.
– Mateusz Piotrowski
1 hour ago

add a comment |

Oh, yeah. This is indded a very handy variation of the script I included in my question. I was afraid that the utility I am looking for does not exist since its functionality is already available with a relatively short sh(1) oneliner.
– Mateusz Piotrowski
1 hour ago

Oh, yeah. This is indded a very handy variation of the script I included in my question. I was afraid that the utility I am looking for does not exist since its functionality is already available with a relatively short sh(1) oneliner.
– Mateusz Piotrowski
1 hour ago

add a comment |

up vote
1
down vote

You could use a subshell:

$ pwd
/home/user
$ (cd /bin && pwd)
/bin
$ pwd
/home/user

A possible downside of this approach is that the values of the variables are not preserved in the parent shell, but it may be useful in certain cases:

$ var=foo; echo "$var"
foo
$ (var=bar; echo "$var")
bar
$ echo "$var"
foo

answered 53 mins ago

nxnev

2,5482423

A subshell is not a solution. It is not a utility and unfortunately it cannot be chained the way you can chain env(1)-like variables.
– Mateusz Piotrowski
42 mins ago

@MateuszPiotrowski Would this approach be valid if you put the entire chain of commands within the subshell? If I understand correctly, it will be basically the same as having a separate script or explicitly calling another interpreter, at least in a shell context.
– nxnev
32 mins ago

In a way, yes. In order to use a subshell we have to be in a shell of some sort. In case you'd like to feed this command to execve you'd have to wrap your subshell in sh -c anyway.
– Mateusz Piotrowski
21 mins ago

add a comment |

up vote
1
down vote

You could use a subshell:

$ pwd
/home/user
$ (cd /bin && pwd)
/bin
$ pwd
/home/user

A possible downside of this approach is that the values of the variables are not preserved in the parent shell, but it may be useful in certain cases:

$ var=foo; echo "$var"
foo
$ (var=bar; echo "$var")
bar
$ echo "$var"
foo

answered 53 mins ago

nxnev

2,5482423

A subshell is not a solution. It is not a utility and unfortunately it cannot be chained the way you can chain env(1)-like variables.
– Mateusz Piotrowski
42 mins ago

@MateuszPiotrowski Would this approach be valid if you put the entire chain of commands within the subshell? If I understand correctly, it will be basically the same as having a separate script or explicitly calling another interpreter, at least in a shell context.
– nxnev
32 mins ago

In a way, yes. In order to use a subshell we have to be in a shell of some sort. In case you'd like to feed this command to execve you'd have to wrap your subshell in sh -c anyway.
– Mateusz Piotrowski
21 mins ago

add a comment |

up vote
1
down vote

You could use a subshell:

$ pwd
/home/user
$ (cd /bin && pwd)
/bin
$ pwd
/home/user

A possible downside of this approach is that the values of the variables are not preserved in the parent shell, but it may be useful in certain cases:

$ var=foo; echo "$var"
foo
$ (var=bar; echo "$var")
bar
$ echo "$var"
foo

answered 53 mins ago

nxnev

2,5482423

You could use a subshell:

$ pwd
/home/user
$ (cd /bin && pwd)
/bin
$ pwd
/home/user

A possible downside of this approach is that the values of the variables are not preserved in the parent shell, but it may be useful in certain cases:

$ var=foo; echo "$var"
foo
$ (var=bar; echo "$var")
bar
$ echo "$var"
foo

answered 53 mins ago

nxnev

2,5482423

answered 53 mins ago

nxnev

2,5482423

answered 53 mins ago

nxnev

2,5482423

answered 53 mins ago

nxnev

2,5482423

A subshell is not a solution. It is not a utility and unfortunately it cannot be chained the way you can chain env(1)-like variables.
– Mateusz Piotrowski
42 mins ago

@MateuszPiotrowski Would this approach be valid if you put the entire chain of commands within the subshell? If I understand correctly, it will be basically the same as having a separate script or explicitly calling another interpreter, at least in a shell context.
– nxnev
32 mins ago

In a way, yes. In order to use a subshell we have to be in a shell of some sort. In case you'd like to feed this command to execve you'd have to wrap your subshell in sh -c anyway.
– Mateusz Piotrowski
21 mins ago

add a comment |

A subshell is not a solution. It is not a utility and unfortunately it cannot be chained the way you can chain env(1)-like variables.
– Mateusz Piotrowski
42 mins ago

@MateuszPiotrowski Would this approach be valid if you put the entire chain of commands within the subshell? If I understand correctly, it will be basically the same as having a separate script or explicitly calling another interpreter, at least in a shell context.
– nxnev
32 mins ago

In a way, yes. In order to use a subshell we have to be in a shell of some sort. In case you'd like to feed this command to execve you'd have to wrap your subshell in sh -c anyway.
– Mateusz Piotrowski
21 mins ago

A subshell is not a solution. It is not a utility and unfortunately it cannot be chained the way you can chain env(1)-like variables.
– Mateusz Piotrowski
42 mins ago

@MateuszPiotrowski Would this approach be valid if you put the entire chain of commands within the subshell? If I understand correctly, it will be basically the same as having a separate script or explicitly calling another interpreter, at least in a shell context.
– nxnev
32 mins ago

In a way, yes. In order to use a subshell we have to be in a shell of some sort. In case you'd like to feed this command to execve you'd have to wrap your subshell in sh -c anyway.
– Mateusz Piotrowski
21 mins ago

add a comment |

up vote
0
down vote

The toolsets used in the daemontools world, and elsewhere, have this and more besides; have had for many years; and are widely available.

Wayne Marshall's perp has runtool:
```
runtool -c /new/cwd myProgram
```

Laurent Bercot's execline has cd:
```
cd /new/cwd myProgram
```

my nosh toolset has chdir:
```
chdir /new/cwd myProgram
```

All of these are chain-loading tools, designed to be used in exactly these sorts of chains. There is a wide selection of chain-loading tools in these toolkits for other purposes.

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