Regex for string not ending with given suffix

Question

I have not been able to find a proper regex to match any string not ending with some condition  For example  I don t want to match anything ending with an a   This matches  b ab 1   This doesn t match  a ba   I know the regex should be ending with   to mark the end  though I don t know what should preceed it   Edit  The original question doesn t seem to be a legit example for my case  So  how to handle more than one character  Say anything not ending with ab   I ve been able to fix this  using this thread           ab        Though the downside with this is  it doesn t match a string of one character

User · Answer

The question is old but I could not find a better solution I post mine here. Find all USB drives but not listing the partitions, thus removing the "part[0-9]" from the results. I ended up doing two grep, the last negates the result:

ls -1 /dev/disk/by-path/* | grep -P "\-usb\-" | grep -vE "part[0-9]*$"

This results on my system:

pci-0000:00:0b.0-usb-0:1:1.0-scsi-0:0:0:0

If I only want the partitions I could do:

ls -1 /dev/disk/by-path/* | grep -P "\-usb\-" | grep -E "part[0-9]*$"

Where I get:

pci-0000:00:0b.0-usb-0:1:1.0-scsi-0:0:0:0-part1
pci-0000:00:0b.0-usb-0:1:1.0-scsi-0:0:0:0-part2

And when I do:

readlink -f /dev/disk/by-path/pci-0000:00:0b.0-usb-0:1:1.0-scsi-0:0:0:0

I get:

/dev/sdb

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To search for files not ending with   tmp  we use the following regex             tmp        Tested with the Regex Tester gives following result

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Try this       a      The    denotes a character class  and the   inverts the character class to match everything but an a

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a     the regex above will match strings which is not ending with a

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If you are using grep or sed the syntax will be a little different  Notice that the sequential   a   b  method does not work here   balter spectre3    printf  jd8a n8 fb nq c n  jd8a 8 fb q c balter spectre3    printf  jd8a n8 fb nq c n    grep      a    8 fb q c balter spectre3    printf  jd8a n8 fb nq c n    grep      b    jd8a q c balter spectre3    printf  jd8a n8 fb nq c n    grep      c    jd8a 8 fb balter spectre3    printf  jd8a n8 fb nq c n    grep      a   b    jd8a q c balter spectre3    printf  jd8a n8 fb nq c n    grep      a   c    jd8a 8 fb balter spectre3    printf  jd8a n8 fb nq c n    grep      a b    q c balter spectre3    printf  jd8a n8 fb nq c n    grep      a c    8 fb balter spectre3    printf  jd8a n8 fb nq c n    grep      b c    jd8a balter spectre3    printf  jd8a n8 fb nq c n    grep      b c a      FWIW  I m finding the same results in Regex101  which I think is JavaScript syntax   Bad  https   regex101 com r MJGAmX 2 Good  https   regex101 com r LzrIBu 2

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Anything that matches something ending with a ---   a  So when you match the regex  negate the condition or alternatively you can also do     a   where   a  means anything which is not a

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You don t give us the language  but if your regex flavour support look behind assertion  this is what you need        lt  a        lt  a  is a negated lookbehind assertion that ensures  that before the end of the string  or row with m modifier   there is not the character  a    See it here on Regexr  You can also easily extend this with other characters  since this checking for the string and isn t a character class        lt  ab     This would match anything that does not end with  ab   see it on Regexr

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Use the not     symbol       a     If you put the   symbol at the beginning of brackets  it means  everything except the things in the brackets     is simply an anchor to the end   For multiple characters  just put them all in their own character set       a   b

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The accepted answer is fine if you can use lookarounds  However  there is also another approach to solve this problem   If we look at the widely proposed regex for this question       a    We will find that it almost works  It does not accept an empty string  which might be a little inconvinient  However  this is a minor issue when dealing with just a one character  However  if we want to exclude whole string  e g   abc   then       a   b   c    won t do  It won t accept ac  for example   There is an easy solution for this problem though  We can simply say      2       a   b   c    or more generalized version      n-1       firstchar   secondchar   where n is length of the string you want forbid  for abc it s 3   and firstchar  secondchar      are first  second     nth characters of your string  for abc it would be a  then b  then c    This comes from a simple observation that a string that is shorter than the text we won t forbid can not contain this text by definition  So we can either accept anything that is shorter  ab  isn t  abc    or anything long enough for us to accept but without the ending   Here s an example of find that will delete all files that are not  jpg   find   -regex     3           j   p   g    -delete

[regex] Regex for string not ending with given suffix

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