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try/finally with bash shell

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try/finally with bash shell

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1

I have these three lines:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 "$cmd" "$@" | bunion
 rm -f "$bunion_uds_file"

I need to make sure the last line always executes..I could do this:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 (
 set +e
 "$cmd" "$@" | bunion
 rm -f "$bunion_uds_file"
 )

or maybe like this:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 "$cmd" "$@" | bunion && rm -f "$bunion_uds_file" || rm -f "$bunion_uds_file"

I assume creating the subshell and using set +e is slightly less performant etc.

bash shell exit-status

share|improve this question

edited 7 hours ago

Kusalananda♦

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asked 8 hours ago

Alexander MillsAlexander Mills

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• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The common practice is to remove a unix domain socket before binding to it. No try/finally, traps, etc could guard against your script just crashing or being killed by SIGKILL. Then the next instance will fail with EADDRINUSE when trying to bind to it.
  
  – mosvy
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Possible duplicate of Getting "ensure" / "finally" functionality in a shell command (not script)?
  
  – muru
  3 hours ago
  

  
  
  
  

add a comment | 

1

I have these three lines:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 "$cmd" "$@" | bunion
 rm -f "$bunion_uds_file"

I need to make sure the last line always executes..I could do this:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 (
 set +e
 "$cmd" "$@" | bunion
 rm -f "$bunion_uds_file"
 )

or maybe like this:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 "$cmd" "$@" | bunion && rm -f "$bunion_uds_file" || rm -f "$bunion_uds_file"

I assume creating the subshell and using set +e is slightly less performant etc.

bash shell exit-status

share|improve this question

edited 7 hours ago

Kusalananda♦

159k1818 gold badges314314 silver badges500500 bronze badges

asked 8 hours ago

Alexander MillsAlexander Mills

2,48722 gold badges2222 silver badges6767 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The common practice is to remove a unix domain socket before binding to it. No try/finally, traps, etc could guard against your script just crashing or being killed by SIGKILL. Then the next instance will fail with EADDRINUSE when trying to bind to it.
  
  – mosvy
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Possible duplicate of Getting "ensure" / "finally" functionality in a shell command (not script)?
  
  – muru
  3 hours ago
  

  
  
  
  

add a comment | 

I have these three lines:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 "$cmd" "$@" | bunion
 rm -f "$bunion_uds_file"

I need to make sure the last line always executes..I could do this:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 (
 set +e
 "$cmd" "$@" | bunion
 rm -f "$bunion_uds_file"
 )

or maybe like this:

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 "$cmd" "$@" | bunion && rm -f "$bunion_uds_file" || rm -f "$bunion_uds_file"

I assume creating the subshell and using set +e is slightly less performant etc.

bash shell exit-status

share|improve this question

edited 7 hours ago

Kusalananda♦

159k1818 gold badges314314 silver badges500500 bronze badges

asked 8 hours ago

Alexander MillsAlexander Mills

2,48722 gold badges2222 silver badges6767 bronze badges

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 "$cmd" "$@" | bunion
 rm -f "$bunion_uds_file"

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 (
 set +e
 "$cmd" "$@" | bunion
 rm -f "$bunion_uds_file"
 )

 export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
 "$cmd" "$@" | bunion && rm -f "$bunion_uds_file" || rm -f "$bunion_uds_file"

share|improve this question

edited 7 hours ago

Kusalananda♦

159k1818 gold badges314314 silver badges500500 bronze badges

asked 8 hours ago

Alexander MillsAlexander Mills

2,48722 gold badges2222 silver badges6767 bronze badges

share|improve this question

edited 7 hours ago

Kusalananda♦

159k1818 gold badges314314 silver badges500500 bronze badges

asked 8 hours ago

Alexander MillsAlexander Mills

2,48722 gold badges2222 silver badges6767 bronze badges

edited 7 hours ago

Kusalananda♦

159k1818 gold badges314314 silver badges500500 bronze badges

edited 7 hours ago

Kusalananda♦

159k1818 gold badges314314 silver badges500500 bronze badges

asked 8 hours ago

Alexander MillsAlexander Mills

2,48722 gold badges2222 silver badges6767 bronze badges

asked 8 hours ago

Alexander MillsAlexander Mills

2,48722 gold badges2222 silver badges6767 bronze badges

1 Answer
1

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oldest

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3

You could set a trap:

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
trap 'rm -f "$bunion_uds_file"' EXIT

"$cmd" "$@" | bunion

This would make the rm -f command run whenever the shell session terminates, except for when terminating by the KILL signal.

As mosvy points out in comments, if this is a socket that needs to be cleaned up before use, it would be easier to remove it before recreating and using it:

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
rm -f "$bunion_uds_file" || exit 1

"$cmd" "$@" | bunion

share|improve this answer

edited 7 hours ago

answered 8 hours ago

Kusalananda♦Kusalananda

159k1818 gold badges314314 silver badges500500 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I like to put the trap code in a function: cleanup() rm -f $thefile; and then trap cleanup EXIT -- I think it's cleaner, and it solves any quoting problems.
  
  – glenn jackman
  7 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @glennjackman You've just introduced a quoting problem in that comment's code, but I get what you're saying. For just deleting a single file in a three line script, I personally think not using a function is ok.
  
  – Kusalananda♦
  7 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes, bash (but not dash or zsh) will also call the EXIT trap when being killed by a SIGINT or SIGTERM, but I don't know how wise it is to rely on that.
  
  – mosvy
  7 hours ago
  

  
  
  
  

add a comment | 

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3

You could set a trap:

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
trap 'rm -f "$bunion_uds_file"' EXIT

"$cmd" "$@" | bunion

This would make the rm -f command run whenever the shell session terminates, except for when terminating by the KILL signal.

As mosvy points out in comments, if this is a socket that needs to be cleaned up before use, it would be easier to remove it before recreating and using it:

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
rm -f "$bunion_uds_file" || exit 1

"$cmd" "$@" | bunion

share|improve this answer

edited 7 hours ago

answered 8 hours ago

Kusalananda♦Kusalananda

159k1818 gold badges314314 silver badges500500 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I like to put the trap code in a function: cleanup() rm -f $thefile; and then trap cleanup EXIT -- I think it's cleaner, and it solves any quoting problems.
  
  – glenn jackman
  7 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @glennjackman You've just introduced a quoting problem in that comment's code, but I get what you're saying. For just deleting a single file in a three line script, I personally think not using a function is ok.
  
  – Kusalananda♦
  7 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes, bash (but not dash or zsh) will also call the EXIT trap when being killed by a SIGINT or SIGTERM, but I don't know how wise it is to rely on that.
  
  – mosvy
  7 hours ago
  

  
  
  
  

add a comment | 

3

You could set a trap:

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
trap 'rm -f "$bunion_uds_file"' EXIT

"$cmd" "$@" | bunion

This would make the rm -f command run whenever the shell session terminates, except for when terminating by the KILL signal.

As mosvy points out in comments, if this is a socket that needs to be cleaned up before use, it would be easier to remove it before recreating and using it:

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
rm -f "$bunion_uds_file" || exit 1

"$cmd" "$@" | bunion

share|improve this answer

edited 7 hours ago

answered 8 hours ago

Kusalananda♦Kusalananda

159k1818 gold badges314314 silver badges500500 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I like to put the trap code in a function: cleanup() rm -f $thefile; and then trap cleanup EXIT -- I think it's cleaner, and it solves any quoting problems.
  
  – glenn jackman
  7 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @glennjackman You've just introduced a quoting problem in that comment's code, but I get what you're saying. For just deleting a single file in a three line script, I personally think not using a function is ok.
  
  – Kusalananda♦
  7 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes, bash (but not dash or zsh) will also call the EXIT trap when being killed by a SIGINT or SIGTERM, but I don't know how wise it is to rely on that.
  
  – mosvy
  7 hours ago
  

  
  
  
  

add a comment | 

You could set a trap:

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
trap 'rm -f "$bunion_uds_file"' EXIT

"$cmd" "$@" | bunion

This would make the rm -f command run whenever the shell session terminates, except for when terminating by the KILL signal.

As mosvy points out in comments, if this is a socket that needs to be cleaned up before use, it would be easier to remove it before recreating and using it:

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
rm -f "$bunion_uds_file" || exit 1

"$cmd" "$@" | bunion

share|improve this answer

edited 7 hours ago

answered 8 hours ago

Kusalananda♦Kusalananda

159k1818 gold badges314314 silver badges500500 bronze badges

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
trap 'rm -f "$bunion_uds_file"' EXIT

"$cmd" "$@" | bunion

#!/bin/bash

export bunion_uds_file="$bunion_socks/$(uuidgen).sock";
rm -f "$bunion_uds_file" || exit 1

"$cmd" "$@" | bunion

share|improve this answer

edited 7 hours ago

answered 8 hours ago

Kusalananda♦Kusalananda

159k1818 gold badges314314 silver badges500500 bronze badges

answered 8 hours ago

Kusalananda♦Kusalananda

159k1818 gold badges314314 silver badges500500 bronze badges

answered 8 hours ago

Kusalananda♦Kusalananda

159k1818 gold badges314314 silver badges500500 bronze badges