Comparing the time of a symlink












3















I want to check whether link lnkfile is older than a regular reference file reffile.



The bash test builtin dereferences links, so test lnkfile -ot reffile compares the target of lnkfile, not the link itself.



Is there a way to make the test builtin not follow symlinks? Otherwise, how can I compare the time of a symlink?






bash shell-script symlink timestamps







share|improve this question





























    3















    I want to check whether link lnkfile is older than a regular reference file reffile.



    The bash test builtin dereferences links, so test lnkfile -ot reffile compares the target of lnkfile, not the link itself.



    Is there a way to make the test builtin not follow symlinks? Otherwise, how can I compare the time of a symlink?






    bash shell-script symlink timestamps







    share|improve this question



























      3












      3








      3








      I want to check whether link lnkfile is older than a regular reference file reffile.



      The bash test builtin dereferences links, so test lnkfile -ot reffile compares the target of lnkfile, not the link itself.



      Is there a way to make the test builtin not follow symlinks? Otherwise, how can I compare the time of a symlink?






      bash shell-script symlink timestamps







      share|improve this question
















      I want to check whether link lnkfile is older than a regular reference file reffile.



      The bash test builtin dereferences links, so test lnkfile -ot reffile compares the target of lnkfile, not the link itself.



      Is there a way to make the test builtin not follow symlinks? Otherwise, how can I compare the time of a symlink?






      bash shell-script symlink timestamps




      bash shell-script symlink timestamps






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 4 hours ago









      Jeff Schaller

      39.7k1054126




      39.7k1054126










      asked 5 hours ago









      L. LevrelL. Levrel

      1,167412




      1,167412






















          2 Answers
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          As far as I know, bash doesn't offer any versions of -ot (and the like) which avoid dereferencing symlinks.



          What you can do instead is use GNU stat (which doesn't dereference symbolic links without -L) and compare their mtime epochs numerically:



          if (( "$(stat --format=%Z lnkfile)" < "$(stat --format=%Z reffile)" )); then
          
    # lnkfile is older
          
fi





          share|improve this answer































            0














            I don't think there is a way with test, but you could use find.



            test "$(find lnkfile ! -newer reffile)" && command


            Here, find returns output if lnkfile is older than reffile. test without an option is equivalent to test -n. This is true if the length of the string is nonzero. Hence, if there is output from find, command is executed.






            share|improve this answer


























            • What test implementation do you have that does not have -n? It's a standard option... Also quote the command substitution.

              – Kusalananda
              4 hours ago













            • @Kusalananda I'm just confirming that no options is identical to -n, so it's easier to grep the man. Good point with the quote. Thanks.

              – Sparhawk
              4 hours ago













            • I misunderstood what you were saying about -n and read it as "there is no -n option" instead of "test without an option is the same as test -n".

              – Kusalananda
              3 hours ago











            • @Kusalananda Ah got it. I edited to clarify my ambiguous language. Thanks again.

              – Sparhawk
              2 hours ago











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            2 Answers
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            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            2














            As far as I know, bash doesn't offer any versions of -ot (and the like) which avoid dereferencing symlinks.



            What you can do instead is use GNU stat (which doesn't dereference symbolic links without -L) and compare their mtime epochs numerically:



            if (( "$(stat --format=%Z lnkfile)" < "$(stat --format=%Z reffile)" )); then
            
    # lnkfile is older
            
fi





            share|improve this answer




























              2














              As far as I know, bash doesn't offer any versions of -ot (and the like) which avoid dereferencing symlinks.



              What you can do instead is use GNU stat (which doesn't dereference symbolic links without -L) and compare their mtime epochs numerically:



              if (( "$(stat --format=%Z lnkfile)" < "$(stat --format=%Z reffile)" )); then
              
    # lnkfile is older
              
fi





              share|improve this answer


























                2












                2








                2







                As far as I know, bash doesn't offer any versions of -ot (and the like) which avoid dereferencing symlinks.



                What you can do instead is use GNU stat (which doesn't dereference symbolic links without -L) and compare their mtime epochs numerically:



                if (( "$(stat --format=%Z lnkfile)" < "$(stat --format=%Z reffile)" )); then
                
    # lnkfile is older
                
fi





                share|improve this answer













                As far as I know, bash doesn't offer any versions of -ot (and the like) which avoid dereferencing symlinks.



                What you can do instead is use GNU stat (which doesn't dereference symbolic links without -L) and compare their mtime epochs numerically:



                if (( "$(stat --format=%Z lnkfile)" < "$(stat --format=%Z reffile)" )); then
                
    # lnkfile is older
                
fi






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 5 hours ago









                Chris DownChris Down

                79.7k14188202




                79.7k14188202

























                    0














                    I don't think there is a way with test, but you could use find.



                    test "$(find lnkfile ! -newer reffile)" && command


                    Here, find returns output if lnkfile is older than reffile. test without an option is equivalent to test -n. This is true if the length of the string is nonzero. Hence, if there is output from find, command is executed.






                    share|improve this answer


























                    • What test implementation do you have that does not have -n? It's a standard option... Also quote the command substitution.

                      – Kusalananda
                      4 hours ago













                    • @Kusalananda I'm just confirming that no options is identical to -n, so it's easier to grep the man. Good point with the quote. Thanks.

                      – Sparhawk
                      4 hours ago













                    • I misunderstood what you were saying about -n and read it as "there is no -n option" instead of "test without an option is the same as test -n".

                      – Kusalananda
                      3 hours ago











                    • @Kusalananda Ah got it. I edited to clarify my ambiguous language. Thanks again.

                      – Sparhawk
                      2 hours ago
















                    0














                    I don't think there is a way with test, but you could use find.



                    test "$(find lnkfile ! -newer reffile)" && command


                    Here, find returns output if lnkfile is older than reffile. test without an option is equivalent to test -n. This is true if the length of the string is nonzero. Hence, if there is output from find, command is executed.






                    share|improve this answer


























                    • What test implementation do you have that does not have -n? It's a standard option... Also quote the command substitution.

                      – Kusalananda
                      4 hours ago













                    • @Kusalananda I'm just confirming that no options is identical to -n, so it's easier to grep the man. Good point with the quote. Thanks.

                      – Sparhawk
                      4 hours ago













                    • I misunderstood what you were saying about -n and read it as "there is no -n option" instead of "test without an option is the same as test -n".

                      – Kusalananda
                      3 hours ago











                    • @Kusalananda Ah got it. I edited to clarify my ambiguous language. Thanks again.

                      – Sparhawk
                      2 hours ago














                    0












                    0








                    0







                    I don't think there is a way with test, but you could use find.



                    test "$(find lnkfile ! -newer reffile)" && command


                    Here, find returns output if lnkfile is older than reffile. test without an option is equivalent to test -n. This is true if the length of the string is nonzero. Hence, if there is output from find, command is executed.






                    share|improve this answer















                    I don't think there is a way with test, but you could use find.



                    test "$(find lnkfile ! -newer reffile)" && command


                    Here, find returns output if lnkfile is older than reffile. test without an option is equivalent to test -n. This is true if the length of the string is nonzero. Hence, if there is output from find, command is executed.







                    share|improve this answer














                    share|improve this answer



                    share|improve this answer








                    edited 2 hours ago

























                    answered 5 hours ago









                    SparhawkSparhawk

                    9,48263992




                    9,48263992













                    • What test implementation do you have that does not have -n? It's a standard option... Also quote the command substitution.

                      – Kusalananda
                      4 hours ago













                    • @Kusalananda I'm just confirming that no options is identical to -n, so it's easier to grep the man. Good point with the quote. Thanks.

                      – Sparhawk
                      4 hours ago













                    • I misunderstood what you were saying about -n and read it as "there is no -n option" instead of "test without an option is the same as test -n".

                      – Kusalananda
                      3 hours ago











                    • @Kusalananda Ah got it. I edited to clarify my ambiguous language. Thanks again.

                      – Sparhawk
                      2 hours ago



















                    • What test implementation do you have that does not have -n? It's a standard option... Also quote the command substitution.

                      – Kusalananda
                      4 hours ago













                    • @Kusalananda I'm just confirming that no options is identical to -n, so it's easier to grep the man. Good point with the quote. Thanks.

                      – Sparhawk
                      4 hours ago













                    • I misunderstood what you were saying about -n and read it as "there is no -n option" instead of "test without an option is the same as test -n".

                      – Kusalananda
                      3 hours ago











                    • @Kusalananda Ah got it. I edited to clarify my ambiguous language. Thanks again.

                      – Sparhawk
                      2 hours ago

















                    What test implementation do you have that does not have -n? It's a standard option... Also quote the command substitution.

                    – Kusalananda
                    4 hours ago







                    What test implementation do you have that does not have -n? It's a standard option... Also quote the command substitution.

                    – Kusalananda
                    4 hours ago















                    @Kusalananda I'm just confirming that no options is identical to -n, so it's easier to grep the man. Good point with the quote. Thanks.

                    – Sparhawk
                    4 hours ago







                    @Kusalananda I'm just confirming that no options is identical to -n, so it's easier to grep the man. Good point with the quote. Thanks.

                    – Sparhawk
                    4 hours ago















                    I misunderstood what you were saying about -n and read it as "there is no -n option" instead of "test without an option is the same as test -n".

                    – Kusalananda
                    3 hours ago





                    I misunderstood what you were saying about -n and read it as "there is no -n option" instead of "test without an option is the same as test -n".

                    – Kusalananda
                    3 hours ago













                    @Kusalananda Ah got it. I edited to clarify my ambiguous language. Thanks again.

                    – Sparhawk
                    2 hours ago





                    @Kusalananda Ah got it. I edited to clarify my ambiguous language. Thanks again.

                    – Sparhawk
                    2 hours ago


















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