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7

1

I just wanted to ask whether there is any command which would work on common shells (bash, dash, kornshell)? It is supposed to check if the line variable contains any part of the path.

if [[ $line =~ "$PWD"$ ]] ;then

shell regular-expression string

share|improve this question

edited Mar 27 '15 at 23:01

Gilles

577k140140 gold badges11901190 silver badges17021702 bronze badges

asked Mar 27 '15 at 12:52

applenicapplenic

18133 gold badges44 silver badges1313 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Did you try this? That command will work in modern bash shells just the way you typed it.
  
  – terdon♦
  Mar 27 '15 at 12:57
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That won't work in dash.
  
  – Jonathan Leffler
  Mar 27 '15 at 14:06
  

  
  
  
  

add a comment
 | 

7

1

I just wanted to ask whether there is any command which would work on common shells (bash, dash, kornshell)? It is supposed to check if the line variable contains any part of the path.

if [[ $line =~ "$PWD"$ ]] ;then

shell regular-expression string

share|improve this question

edited Mar 27 '15 at 23:01

Gilles

577k140140 gold badges11901190 silver badges17021702 bronze badges

asked Mar 27 '15 at 12:52

applenicapplenic

18133 gold badges44 silver badges1313 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Did you try this? That command will work in modern bash shells just the way you typed it.
  
  – terdon♦
  Mar 27 '15 at 12:57
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That won't work in dash.
  
  – Jonathan Leffler
  Mar 27 '15 at 14:06
  

  
  
  
  

add a comment
 | 

I just wanted to ask whether there is any command which would work on common shells (bash, dash, kornshell)? It is supposed to check if the line variable contains any part of the path.

if [[ $line =~ "$PWD"$ ]] ;then

shell regular-expression string

share|improve this question

edited Mar 27 '15 at 23:01

Gilles

577k140140 gold badges11901190 silver badges17021702 bronze badges

asked Mar 27 '15 at 12:52

applenicapplenic

18133 gold badges44 silver badges1313 bronze badges

if [[ $line =~ "$PWD"$ ]] ;then

share|improve this question

edited Mar 27 '15 at 23:01

Gilles

577k140140 gold badges11901190 silver badges17021702 bronze badges

asked Mar 27 '15 at 12:52

applenicapplenic

18133 gold badges44 silver badges1313 bronze badges

share|improve this question

edited Mar 27 '15 at 23:01

Gilles

577k140140 gold badges11901190 silver badges17021702 bronze badges

asked Mar 27 '15 at 12:52

applenicapplenic

18133 gold badges44 silver badges1313 bronze badges

edited Mar 27 '15 at 23:01

Gilles

577k140140 gold badges11901190 silver badges17021702 bronze badges

edited Mar 27 '15 at 23:01

Gilles

577k140140 gold badges11901190 silver badges17021702 bronze badges

asked Mar 27 '15 at 12:52

applenicapplenic

18133 gold badges44 silver badges1313 bronze badges

asked Mar 27 '15 at 12:52

applenicapplenic

18133 gold badges44 silver badges1313 bronze badges

2 Answers
2

active

oldest

votes

6

Yes, recent versions of bash can do this:

$ pwd

/home/terdon

$ line="I'm in /home/terdon"

$ [[ "$line" =~ "$PWD"$ ]] && echo yes

yes

The same syntax works in zsh and ksh but not in dash. As far as I know, dash has no such capabilities.

Note that regexp finds copied expansion $PWD as tail $anchored in literal copied expansion $line (maybe discounting 001 (start of transmission) but this editionist has not the time or derision to revisit that glaring omission to computational order since fixing printf for any rwongs in evidence).

similarly: <${line##*"$PWD"}>.||shite()?

if only the peace treaties and must be this high to fly could accredit to our visionary free thinking computer masterminds of self aggrandizing language defecations. but we could just party!

... ahem ...

hecking whether the variable $line ends with $PWD. To check if $PWD matches anywhere in $line, remove the $:

$ line="I'm in /home/terdon, are you?"

$ [[ "$line" =~ "$PWD" ]] && echo yes

yes

share|improve this answer

edited 20 mins ago

mikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

answered Mar 27 '15 at 12:57

terdon♦terdon

143k3535 gold badges295295 silver badges472472 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  No, those only work in bash-3.2 and above provided the compat31 option has not been enabled or ksh93. It won't work properly in other bash versions or zsh if $PWD contains regular expression operators.
  
  – Stéphane Chazelas
  Mar 29 '15 at 21:34
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas yes, that's why I specified that recent versions of bash can do this. As for the rest, I just tried it in /home/terdon/foo with zsh, ksh and bash (4.3.25) and it worked fine with all of them. It does indeed break when PWD contains regex operators. That had simply never occurred to me, thanks!
  
  – terdon♦
  Mar 29 '15 at 22:51
  

  
  
  
  

add a comment
 | 

11

In any POSIX-compatible shell you can do:

case $line in (*"$PWD"*)

#    whatever your then block had

;;esac

This works in bash, dash, and just about any other shell you can name.

It can also be used to handle multiple possibilities easily. For example:

case $line in 

(*"$PWD"*)

    echo $PWD match!

;;

(*"$OLDPWD"*)

    echo $OLDPWD match!

;;

(*)

    ! echo no match!

;;esac

You can also use alternation:

case $line in (*"$PWD"*|*"$OLDPWD"*)

    echo '$OLDPWD|$PWD match!'

;;esac

Note the use of quoting above:

1. 
   case $line ...
   
   
   
   • The object of a case statement will not be split on either $IFS or be used as a pattern for filename gen. This is similar to the way the left argument in a [[ test is treated.
   
   
   
   


2. 
   (*"$PWD"*)
   
   
   
   • Here also a shell expansion is not subjected to either $IFS or filename generation - an unquoted expansion will neither split nor glob.
   
   
   • But an unquoted expansion here might be construed as a pattern rather than a literal string though, and so an expansion might mean more than one thing depending on whether or not it is quoted.
   
   
   • It is important to quote any variable used in a pattern that should be literally interpreted, in the same way you would quote pattern chars which you wanted interpreted literally.
   
   
   • For example, if $PWD contained a * and was not quoted it would be construed as a pattern object and not as a literal * to be searched for.
   
   
   
   

share|improve this answer

edited Mar 30 '15 at 10:48

answered Mar 27 '15 at 23:09

mikeservmikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @terdon - you were right - the : comment was confusing, but I used it because it didn't gen a syntax error or accidentally run some proggie named whatever in $PATH. This way will still gen a syntax error, but at least it's kinda clear that it should.
  
  – mikeserv
  Mar 29 '15 at 17:49
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Note that if you need portability with the Bourne shell (for some ancient systems for instance), you need to drop the (: case $line in *"$PWD"*)
  
  – Stéphane Chazelas
  Mar 29 '15 at 21:35
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas - true, but if you do that, zsh chokes on it.
  
  – mikeserv
  Mar 30 '15 at 8:53
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  What do you mean? Are your referring to things like $(case a in a);; esac)?
  
  – Stéphane Chazelas
  Mar 30 '15 at 10:22
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas - I can't reproduce it, unless I do the command sub like in your example. It's weird too - zsh -cx '(case $1 in $2*) echo ok;;esac)' -- one o works, but prefixing a : $ breaks it. I guess that's the problem I encountered in the past - it was always a little unclear, and I never looked at it too hard because adding the leftmost ( always fixed it. Eventually I just wrote it off as some weird zsh thing and made it a rule to use both ends.
  
  – mikeserv
  Mar 30 '15 at 10:32
  
  
  

  
  
  
  

 | 
show 4 more comments

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6

Yes, recent versions of bash can do this:

$ pwd

/home/terdon

$ line="I'm in /home/terdon"

$ [[ "$line" =~ "$PWD"$ ]] && echo yes

yes

The same syntax works in zsh and ksh but not in dash. As far as I know, dash has no such capabilities.

Note that regexp finds copied expansion $PWD as tail $anchored in literal copied expansion $line (maybe discounting 001 (start of transmission) but this editionist has not the time or derision to revisit that glaring omission to computational order since fixing printf for any rwongs in evidence).

similarly: <${line##*"$PWD"}>.||shite()?

if only the peace treaties and must be this high to fly could accredit to our visionary free thinking computer masterminds of self aggrandizing language defecations. but we could just party!

... ahem ...

hecking whether the variable $line ends with $PWD. To check if $PWD matches anywhere in $line, remove the $:

$ line="I'm in /home/terdon, are you?"

$ [[ "$line" =~ "$PWD" ]] && echo yes

yes

share|improve this answer

edited 20 mins ago

mikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

answered Mar 27 '15 at 12:57

terdon♦terdon

143k3535 gold badges295295 silver badges472472 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  No, those only work in bash-3.2 and above provided the compat31 option has not been enabled or ksh93. It won't work properly in other bash versions or zsh if $PWD contains regular expression operators.
  
  – Stéphane Chazelas
  Mar 29 '15 at 21:34
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas yes, that's why I specified that recent versions of bash can do this. As for the rest, I just tried it in /home/terdon/foo with zsh, ksh and bash (4.3.25) and it worked fine with all of them. It does indeed break when PWD contains regex operators. That had simply never occurred to me, thanks!
  
  – terdon♦
  Mar 29 '15 at 22:51
  

  
  
  
  

add a comment
 | 

6

Yes, recent versions of bash can do this:

$ pwd

/home/terdon

$ line="I'm in /home/terdon"

$ [[ "$line" =~ "$PWD"$ ]] && echo yes

yes

The same syntax works in zsh and ksh but not in dash. As far as I know, dash has no such capabilities.

Note that regexp finds copied expansion $PWD as tail $anchored in literal copied expansion $line (maybe discounting 001 (start of transmission) but this editionist has not the time or derision to revisit that glaring omission to computational order since fixing printf for any rwongs in evidence).

similarly: <${line##*"$PWD"}>.||shite()?

if only the peace treaties and must be this high to fly could accredit to our visionary free thinking computer masterminds of self aggrandizing language defecations. but we could just party!

... ahem ...

hecking whether the variable $line ends with $PWD. To check if $PWD matches anywhere in $line, remove the $:

$ line="I'm in /home/terdon, are you?"

$ [[ "$line" =~ "$PWD" ]] && echo yes

yes

share|improve this answer

edited 20 mins ago

mikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

answered Mar 27 '15 at 12:57

terdon♦terdon

143k3535 gold badges295295 silver badges472472 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  No, those only work in bash-3.2 and above provided the compat31 option has not been enabled or ksh93. It won't work properly in other bash versions or zsh if $PWD contains regular expression operators.
  
  – Stéphane Chazelas
  Mar 29 '15 at 21:34
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas yes, that's why I specified that recent versions of bash can do this. As for the rest, I just tried it in /home/terdon/foo with zsh, ksh and bash (4.3.25) and it worked fine with all of them. It does indeed break when PWD contains regex operators. That had simply never occurred to me, thanks!
  
  – terdon♦
  Mar 29 '15 at 22:51
  

  
  
  
  

add a comment
 | 

Yes, recent versions of bash can do this:

$ pwd

/home/terdon

$ line="I'm in /home/terdon"

$ [[ "$line" =~ "$PWD"$ ]] && echo yes

yes

The same syntax works in zsh and ksh but not in dash. As far as I know, dash has no such capabilities.

Note that regexp finds copied expansion $PWD as tail $anchored in literal copied expansion $line (maybe discounting 001 (start of transmission) but this editionist has not the time or derision to revisit that glaring omission to computational order since fixing printf for any rwongs in evidence).

similarly: <${line##*"$PWD"}>.||shite()?

if only the peace treaties and must be this high to fly could accredit to our visionary free thinking computer masterminds of self aggrandizing language defecations. but we could just party!

... ahem ...

hecking whether the variable $line ends with $PWD. To check if $PWD matches anywhere in $line, remove the $:

$ line="I'm in /home/terdon, are you?"

$ [[ "$line" =~ "$PWD" ]] && echo yes

yes

share|improve this answer

edited 20 mins ago

mikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

answered Mar 27 '15 at 12:57

terdon♦terdon

143k3535 gold badges295295 silver badges472472 bronze badges

$ pwd

/home/terdon

$ line="I'm in /home/terdon"

$ [[ "$line" =~ "$PWD"$ ]] && echo yes

yes

$ line="I'm in /home/terdon, are you?"

$ [[ "$line" =~ "$PWD" ]] && echo yes

yes

share|improve this answer

edited 20 mins ago

mikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

answered Mar 27 '15 at 12:57

terdon♦terdon

143k3535 gold badges295295 silver badges472472 bronze badges

edited 20 mins ago

mikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

edited 20 mins ago

mikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

answered Mar 27 '15 at 12:57

terdon♦terdon

143k3535 gold badges295295 silver badges472472 bronze badges

answered Mar 27 '15 at 12:57

terdon♦terdon

143k3535 gold badges295295 silver badges472472 bronze badges

11

In any POSIX-compatible shell you can do:

case $line in (*"$PWD"*)

#    whatever your then block had

;;esac

This works in bash, dash, and just about any other shell you can name.

It can also be used to handle multiple possibilities easily. For example:

case $line in 

(*"$PWD"*)

    echo $PWD match!

;;

(*"$OLDPWD"*)

    echo $OLDPWD match!

;;

(*)

    ! echo no match!

;;esac

You can also use alternation:

case $line in (*"$PWD"*|*"$OLDPWD"*)

    echo '$OLDPWD|$PWD match!'

;;esac

Note the use of quoting above:

1. 
   case $line ...
   
   
   
   • The object of a case statement will not be split on either $IFS or be used as a pattern for filename gen. This is similar to the way the left argument in a [[ test is treated.
   
   
   
   


2. 
   (*"$PWD"*)
   
   
   
   • Here also a shell expansion is not subjected to either $IFS or filename generation - an unquoted expansion will neither split nor glob.
   
   
   • But an unquoted expansion here might be construed as a pattern rather than a literal string though, and so an expansion might mean more than one thing depending on whether or not it is quoted.
   
   
   • It is important to quote any variable used in a pattern that should be literally interpreted, in the same way you would quote pattern chars which you wanted interpreted literally.
   
   
   • For example, if $PWD contained a * and was not quoted it would be construed as a pattern object and not as a literal * to be searched for.
   
   
   
   

share|improve this answer

edited Mar 30 '15 at 10:48

answered Mar 27 '15 at 23:09

mikeservmikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @terdon - you were right - the : comment was confusing, but I used it because it didn't gen a syntax error or accidentally run some proggie named whatever in $PATH. This way will still gen a syntax error, but at least it's kinda clear that it should.
  
  – mikeserv
  Mar 29 '15 at 17:49
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Note that if you need portability with the Bourne shell (for some ancient systems for instance), you need to drop the (: case $line in *"$PWD"*)
  
  – Stéphane Chazelas
  Mar 29 '15 at 21:35
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas - true, but if you do that, zsh chokes on it.
  
  – mikeserv
  Mar 30 '15 at 8:53
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  What do you mean? Are your referring to things like $(case a in a);; esac)?
  
  – Stéphane Chazelas
  Mar 30 '15 at 10:22
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas - I can't reproduce it, unless I do the command sub like in your example. It's weird too - zsh -cx '(case $1 in $2*) echo ok;;esac)' -- one o works, but prefixing a : $ breaks it. I guess that's the problem I encountered in the past - it was always a little unclear, and I never looked at it too hard because adding the leftmost ( always fixed it. Eventually I just wrote it off as some weird zsh thing and made it a rule to use both ends.
  
  – mikeserv
  Mar 30 '15 at 10:32
  
  
  

  
  
  
  

 | 
show 4 more comments

11

In any POSIX-compatible shell you can do:

case $line in (*"$PWD"*)

#    whatever your then block had

;;esac

This works in bash, dash, and just about any other shell you can name.

It can also be used to handle multiple possibilities easily. For example:

case $line in 

(*"$PWD"*)

    echo $PWD match!

;;

(*"$OLDPWD"*)

    echo $OLDPWD match!

;;

(*)

    ! echo no match!

;;esac

You can also use alternation:

case $line in (*"$PWD"*|*"$OLDPWD"*)

    echo '$OLDPWD|$PWD match!'

;;esac

Note the use of quoting above:

1. 
   case $line ...
   
   
   
   • The object of a case statement will not be split on either $IFS or be used as a pattern for filename gen. This is similar to the way the left argument in a [[ test is treated.
   
   
   
   


2. 
   (*"$PWD"*)
   
   
   
   • Here also a shell expansion is not subjected to either $IFS or filename generation - an unquoted expansion will neither split nor glob.
   
   
   • But an unquoted expansion here might be construed as a pattern rather than a literal string though, and so an expansion might mean more than one thing depending on whether or not it is quoted.
   
   
   • It is important to quote any variable used in a pattern that should be literally interpreted, in the same way you would quote pattern chars which you wanted interpreted literally.
   
   
   • For example, if $PWD contained a * and was not quoted it would be construed as a pattern object and not as a literal * to be searched for.
   
   
   
   

share|improve this answer

edited Mar 30 '15 at 10:48

answered Mar 27 '15 at 23:09

mikeservmikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @terdon - you were right - the : comment was confusing, but I used it because it didn't gen a syntax error or accidentally run some proggie named whatever in $PATH. This way will still gen a syntax error, but at least it's kinda clear that it should.
  
  – mikeserv
  Mar 29 '15 at 17:49
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Note that if you need portability with the Bourne shell (for some ancient systems for instance), you need to drop the (: case $line in *"$PWD"*)
  
  – Stéphane Chazelas
  Mar 29 '15 at 21:35
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas - true, but if you do that, zsh chokes on it.
  
  – mikeserv
  Mar 30 '15 at 8:53
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  What do you mean? Are your referring to things like $(case a in a);; esac)?
  
  – Stéphane Chazelas
  Mar 30 '15 at 10:22
  

  
  
  
  


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  @StéphaneChazelas - I can't reproduce it, unless I do the command sub like in your example. It's weird too - zsh -cx '(case $1 in $2*) echo ok;;esac)' -- one o works, but prefixing a : $ breaks it. I guess that's the problem I encountered in the past - it was always a little unclear, and I never looked at it too hard because adding the leftmost ( always fixed it. Eventually I just wrote it off as some weird zsh thing and made it a rule to use both ends.
  
  – mikeserv
  Mar 30 '15 at 10:32
  
  
  

  
  
  
  

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show 4 more comments

In any POSIX-compatible shell you can do:

case $line in (*"$PWD"*)

#    whatever your then block had

;;esac

This works in bash, dash, and just about any other shell you can name.

It can also be used to handle multiple possibilities easily. For example:

case $line in 

(*"$PWD"*)

    echo $PWD match!

;;

(*"$OLDPWD"*)

    echo $OLDPWD match!

;;

(*)

    ! echo no match!

;;esac

You can also use alternation:

case $line in (*"$PWD"*|*"$OLDPWD"*)

    echo '$OLDPWD|$PWD match!'

;;esac

Note the use of quoting above:

1. 
   case $line ...
   
   
   
   • The object of a case statement will not be split on either $IFS or be used as a pattern for filename gen. This is similar to the way the left argument in a [[ test is treated.
   
   
   
   


2. 
   (*"$PWD"*)
   
   
   
   • Here also a shell expansion is not subjected to either $IFS or filename generation - an unquoted expansion will neither split nor glob.
   
   
   • But an unquoted expansion here might be construed as a pattern rather than a literal string though, and so an expansion might mean more than one thing depending on whether or not it is quoted.
   
   
   • It is important to quote any variable used in a pattern that should be literally interpreted, in the same way you would quote pattern chars which you wanted interpreted literally.
   
   
   • For example, if $PWD contained a * and was not quoted it would be construed as a pattern object and not as a literal * to be searched for.
   
   
   
   

share|improve this answer

edited Mar 30 '15 at 10:48

answered Mar 27 '15 at 23:09

mikeservmikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

case $line in (*"$PWD"*)

#    whatever your then block had

;;esac

case $line in 

(*"$PWD"*)

    echo $PWD match!

;;

(*"$OLDPWD"*)

    echo $OLDPWD match!

;;

(*)

    ! echo no match!

;;esac

case $line in (*"$PWD"*|*"$OLDPWD"*)

    echo '$OLDPWD|$PWD match!'

;;esac

share|improve this answer

edited Mar 30 '15 at 10:48

answered Mar 27 '15 at 23:09

mikeservmikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

answered Mar 27 '15 at 23:09

mikeservmikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges

answered Mar 27 '15 at 23:09

mikeservmikeserv

47.3k66 gold badges7373 silver badges173173 bronze badges