Why isn't tilde expansion performed on the input to read?

up vote
6
down vote

favorite

Why has tilde expansion not occurred in the output of this script?

#!/bin/bash



read -p "Enter filename: " fname

if [[ -d $fname ]]

then

        echo "$fname is a directory"

else

        echo "$fname is not a directory"

fi

Output:

$ bash -x test_cd.sh 

+ read -p 'Enter filename: ' fname

Enter filename: ~/Music

+ [[ -d ~/Music ]]

+ echo ' ~/Music is not a directory'

 ~/Music is not a directory

edited Nov 18 at 14:12

Zanna

49.1k13123234

asked Nov 18 at 7:11

jestadi

335

add a comment |

up vote
6
down vote

favorite

Why has tilde expansion not occurred in the output of this script?

#!/bin/bash



read -p "Enter filename: " fname

if [[ -d $fname ]]

then

        echo "$fname is a directory"

else

        echo "$fname is not a directory"

fi

Output:

$ bash -x test_cd.sh 

+ read -p 'Enter filename: ' fname

Enter filename: ~/Music

+ [[ -d ~/Music ]]

+ echo ' ~/Music is not a directory'

 ~/Music is not a directory

edited Nov 18 at 14:12

Zanna

49.1k13123234

asked Nov 18 at 7:11

jestadi

335

add a comment |

up vote
6
down vote

favorite

Why has tilde expansion not occurred in the output of this script?

#!/bin/bash



read -p "Enter filename: " fname

if [[ -d $fname ]]

then

        echo "$fname is a directory"

else

        echo "$fname is not a directory"

fi

Output:

$ bash -x test_cd.sh 

+ read -p 'Enter filename: ' fname

Enter filename: ~/Music

+ [[ -d ~/Music ]]

+ echo ' ~/Music is not a directory'

 ~/Music is not a directory

edited Nov 18 at 14:12

Zanna

49.1k13123234

asked Nov 18 at 7:11

jestadi

335

Why has tilde expansion not occurred in the output of this script?

#!/bin/bash



read -p "Enter filename: " fname

if [[ -d $fname ]]

then

        echo "$fname is a directory"

else

        echo "$fname is not a directory"

fi

Output:

$ bash -x test_cd.sh 

+ read -p 'Enter filename: ' fname

Enter filename: ~/Music

+ [[ -d ~/Music ]]

+ echo ' ~/Music is not a directory'

 ~/Music is not a directory

command-line bash scripts

edited Nov 18 at 14:12

Zanna

49.1k13123234

asked Nov 18 at 7:11

jestadi

335

edited Nov 18 at 14:12

Zanna

49.1k13123234

asked Nov 18 at 7:11

jestadi

335

edited Nov 18 at 14:12

Zanna

49.1k13123234

edited Nov 18 at 14:12

Zanna

49.1k13123234

edited Nov 18 at 14:12

Zanna

49.1k13123234

asked Nov 18 at 7:11

jestadi

335

asked Nov 18 at 7:11

jestadi

335

asked Nov 18 at 7:11

jestadi

335

add a comment |

1 Answer
1

active

oldest

votes

up vote
7
down vote

accepted

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited Nov 18 at 16:50

answered Nov 18 at 7:48

dessert

21.3k55896

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
Nov 18 at 8:08

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
Nov 18 at 14:15

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
Nov 18 at 19:34

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
7
down vote

accepted

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited Nov 18 at 16:50

answered Nov 18 at 7:48

dessert

21.3k55896

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
Nov 18 at 8:08

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
Nov 18 at 14:15

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
Nov 18 at 19:34

add a comment |

up vote
7
down vote

accepted

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited Nov 18 at 16:50

answered Nov 18 at 7:48

dessert

21.3k55896

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
Nov 18 at 8:08

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
Nov 18 at 14:15

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
Nov 18 at 19:34

add a comment |

up vote
7
down vote

accepted

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited Nov 18 at 16:50

answered Nov 18 at 7:48

dessert

21.3k55896

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited Nov 18 at 16:50

answered Nov 18 at 7:48

dessert

21.3k55896

edited Nov 18 at 16:50

answered Nov 18 at 7:48

dessert

21.3k55896

answered Nov 18 at 7:48

dessert

21.3k55896

answered Nov 18 at 7:48

dessert

21.3k55896

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
Nov 18 at 8:08

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
Nov 18 at 14:15

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
Nov 18 at 19:34

add a comment |

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
Nov 18 at 8:08

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
Nov 18 at 14:15

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
Nov 18 at 19:34

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
Nov 18 at 8:08

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
Nov 18 at 14:15

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
Nov 18 at 19:34

add a comment |

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