How to get â€œFOO=bar.cpp meld a/$FOO b/$FOOâ€ to work the way I expect it to?

up vote
1
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As far as I understand, to compare the same file in separate directories I should be able to do this:

FOO=bar.cpp meld a/$FOO b/$FOO

However, it doesn't work, as if $FOO is an empty string. This not surprisingly works:

(FOO=bar.cpp && meld a/$FOO b/$FOO)

My question is why does the first example not work?

edited Feb 27 at 4:02

asked Feb 27 at 3:56

Ken Y-N

1375

Are you sure FOO=bar.cpp echo a/$FOO b/$FOO give you a/$FOO b/$FOO? I think no
â€“Â cuonglm
Feb 27 at 3:59

Oops, I had set FOO globally whilst experimenting - I've deleted that example.
â€“Â Ken Y-N
Feb 27 at 4:03

add a commentÂ |Â

up vote
1
down vote

favorite

As far as I understand, to compare the same file in separate directories I should be able to do this:

FOO=bar.cpp meld a/$FOO b/$FOO

However, it doesn't work, as if $FOO is an empty string. This not surprisingly works:

(FOO=bar.cpp && meld a/$FOO b/$FOO)

My question is why does the first example not work?

edited Feb 27 at 4:02

asked Feb 27 at 3:56

Ken Y-N

1375

Are you sure FOO=bar.cpp echo a/$FOO b/$FOO give you a/$FOO b/$FOO? I think no
â€“Â cuonglm
Feb 27 at 3:59

Oops, I had set FOO globally whilst experimenting - I've deleted that example.
â€“Â Ken Y-N
Feb 27 at 4:03

add a commentÂ |Â

up vote
1
down vote

favorite

As far as I understand, to compare the same file in separate directories I should be able to do this:

FOO=bar.cpp meld a/$FOO b/$FOO

However, it doesn't work, as if $FOO is an empty string. This not surprisingly works:

(FOO=bar.cpp && meld a/$FOO b/$FOO)

My question is why does the first example not work?

edited Feb 27 at 4:02

asked Feb 27 at 3:56

Ken Y-N

1375

As far as I understand, to compare the same file in separate directories I should be able to do this:

FOO=bar.cpp meld a/$FOO b/$FOO

However, it doesn't work, as if $FOO is an empty string. This not surprisingly works:

(FOO=bar.cpp && meld a/$FOO b/$FOO)

My question is why does the first example not work?

edited Feb 27 at 4:02

asked Feb 27 at 3:56

Ken Y-N

1375

edited Feb 27 at 4:02

asked Feb 27 at 3:56

Ken Y-N

1375

asked Feb 27 at 3:56

Ken Y-N

1375

asked Feb 27 at 3:56

Ken Y-N

1375

Are you sure FOO=bar.cpp echo a/$FOO b/$FOO give you a/$FOO b/$FOO? I think no
â€“Â cuonglm
Feb 27 at 3:59

Oops, I had set FOO globally whilst experimenting - I've deleted that example.
â€“Â Ken Y-N
Feb 27 at 4:03

add a commentÂ |Â

Are you sure FOO=bar.cpp echo a/$FOO b/$FOO give you a/$FOO b/$FOO? I think no
â€“Â cuonglm
Feb 27 at 3:59

Oops, I had set FOO globally whilst experimenting - I've deleted that example.
â€“Â Ken Y-N
Feb 27 at 4:03

Are you sure FOO=bar.cpp echo a/$FOO b/$FOO give you a/$FOO b/$FOO? I think no
â€“Â cuonglm
Feb 27 at 3:59

Oops, I had set FOO globally whilst experimenting - I've deleted that example.
â€“Â Ken Y-N
Feb 27 at 4:03

add a commentÂ |Â

1 Answer
1

active

oldest

votes

up vote
3
down vote

accepted

In:

FOO=bar.cpp meld a/$FOO b/$FOO

It's a Simple Command, so FOO=bar.cpp isn't executed at the time $FOO was expanded.

In:

FOO=bar.cpp && meld a/$FOO b/$FOO

There're 2 commands:

FOO=bar.cpp

and:

meld a/$FOO b/$FOO

When parameter substitution performed in meld a/$FOO b/$FOO, FOO=bar.cpp was executed, so FOO was set to bar.cpp.

edited Feb 27 at 4:21

answered Feb 27 at 4:12

cuonglm

97.3k21185278

So basically a Simple Command cannot do what I hoped it could?
â€“Â Ken Y-N
Feb 27 at 4:35

@KenY-N yes, (FOO=bar.cpp; meld "a/$FOO" "b/$FOO") is the way to go if you don't want to FOO retains after command finish. Note the double quotes. You can use any statement termination like ; above instead of &&.
â€“Â cuonglm
Feb 27 at 4:53

add a commentÂ |Â

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
3
down vote

accepted

In:

FOO=bar.cpp meld a/$FOO b/$FOO

It's a Simple Command, so FOO=bar.cpp isn't executed at the time $FOO was expanded.

In:

FOO=bar.cpp && meld a/$FOO b/$FOO

There're 2 commands:

FOO=bar.cpp

and:

meld a/$FOO b/$FOO

When parameter substitution performed in meld a/$FOO b/$FOO, FOO=bar.cpp was executed, so FOO was set to bar.cpp.

edited Feb 27 at 4:21

answered Feb 27 at 4:12

cuonglm

97.3k21185278

So basically a Simple Command cannot do what I hoped it could?
â€“Â Ken Y-N
Feb 27 at 4:35

@KenY-N yes, (FOO=bar.cpp; meld "a/$FOO" "b/$FOO") is the way to go if you don't want to FOO retains after command finish. Note the double quotes. You can use any statement termination like ; above instead of &&.
â€“Â cuonglm
Feb 27 at 4:53

add a commentÂ |Â

up vote
3
down vote

accepted

In:

FOO=bar.cpp meld a/$FOO b/$FOO

It's a Simple Command, so FOO=bar.cpp isn't executed at the time $FOO was expanded.

In:

FOO=bar.cpp && meld a/$FOO b/$FOO

There're 2 commands:

FOO=bar.cpp

and:

meld a/$FOO b/$FOO

When parameter substitution performed in meld a/$FOO b/$FOO, FOO=bar.cpp was executed, so FOO was set to bar.cpp.

edited Feb 27 at 4:21

answered Feb 27 at 4:12

cuonglm

97.3k21185278

So basically a Simple Command cannot do what I hoped it could?
â€“Â Ken Y-N
Feb 27 at 4:35

@KenY-N yes, (FOO=bar.cpp; meld "a/$FOO" "b/$FOO") is the way to go if you don't want to FOO retains after command finish. Note the double quotes. You can use any statement termination like ; above instead of &&.
â€“Â cuonglm
Feb 27 at 4:53

add a commentÂ |Â

up vote
3
down vote

accepted

In:

FOO=bar.cpp meld a/$FOO b/$FOO

It's a Simple Command, so FOO=bar.cpp isn't executed at the time $FOO was expanded.

In:

FOO=bar.cpp && meld a/$FOO b/$FOO

There're 2 commands:

FOO=bar.cpp

and:

meld a/$FOO b/$FOO

When parameter substitution performed in meld a/$FOO b/$FOO, FOO=bar.cpp was executed, so FOO was set to bar.cpp.

edited Feb 27 at 4:21

answered Feb 27 at 4:12

cuonglm

97.3k21185278

In:

FOO=bar.cpp meld a/$FOO b/$FOO

It's a Simple Command, so FOO=bar.cpp isn't executed at the time $FOO was expanded.

In:

FOO=bar.cpp && meld a/$FOO b/$FOO

There're 2 commands:

FOO=bar.cpp

and:

meld a/$FOO b/$FOO

When parameter substitution performed in meld a/$FOO b/$FOO, FOO=bar.cpp was executed, so FOO was set to bar.cpp.

edited Feb 27 at 4:21

answered Feb 27 at 4:12

cuonglm

97.3k21185278

edited Feb 27 at 4:21

answered Feb 27 at 4:12

cuonglm

97.3k21185278

answered Feb 27 at 4:12

cuonglm

97.3k21185278

answered Feb 27 at 4:12

cuonglm

97.3k21185278

So basically a Simple Command cannot do what I hoped it could?
â€“Â Ken Y-N
Feb 27 at 4:35

@KenY-N yes, (FOO=bar.cpp; meld "a/$FOO" "b/$FOO") is the way to go if you don't want to FOO retains after command finish. Note the double quotes. You can use any statement termination like ; above instead of &&.
â€“Â cuonglm
Feb 27 at 4:53

add a commentÂ |Â

So basically a Simple Command cannot do what I hoped it could?
â€“Â Ken Y-N
Feb 27 at 4:35

@KenY-N yes, (FOO=bar.cpp; meld "a/$FOO" "b/$FOO") is the way to go if you don't want to FOO retains after command finish. Note the double quotes. You can use any statement termination like ; above instead of &&.
â€“Â cuonglm
Feb 27 at 4:53

So basically a Simple Command cannot do what I hoped it could?
â€“Â Ken Y-N
Feb 27 at 4:35

@KenY-N yes, (FOO=bar.cpp; meld "a/$FOO" "b/$FOO") is the way to go if you don't want to FOO retains after command finish. Note the double quotes. You can use any statement termination like ; above instead of &&.
â€“Â cuonglm
Feb 27 at 4:53

add a commentÂ |Â

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