Notepad++ regex to find single character bounded by |

Question

I'm having trouble coming up with the regex I need to do this find/replace in Notepad++. I'm fine with needing a couple of separate searches to complete the process.

Basically I need to add a | at the beginning and end of every line from a CSV, plus replace all the , with |. Then, on any value with only 1 character, I need to put two spaces around the character on each side ("A" becomes " A ")

Source:

col1,col2,col3,col4,col5,col6
name,desc,something,else,here,too
another,,three,,,
single,characters,here,a,b,c
last,line,here,,almost,

Results:

|col1|col2|col3|col4|col5|col6|
|name|desc|something|else|here|too|
|another||three||||
|single|characters|here|  a  |  b  |  c  |
|last|line|here||almost||

Adding the | to the beginning and the end of the line is simple enough, and replacing , with | is obviously straightforward. But I can't come up with the regex to find |x| where x is limited to a single character. I'm sure it is simple, but I'm new to regex.

revo · Accepted Answer · 2016-10-09T10:08:53.630

4

Regex:

(?:(^)|(?!^)\G)(?:([^\r\n,]{2,})|([^\r\n,]))?(?:(,$)|(,)|($))

Replacement string:

(?{1}|)(?{2}\2)(?{3}  \3  )(?{4}||)(?{5}|)(?{6}|)

Ugly, dirty and long but works.

Regex Explanation:

(?:                 # Start of non-capturing group (a)
    (^)                 # Assert beginning of line (CP #1)
    |                   # Or
    (?!^)               # //
    \G                  # Match at previous matched position
)                   # End of non-capturing group (a)

(?:                 # Start of non-capturing group (b)
    ([^\r\n,]{2,})      # Match characters with more than 2-char length (any except \r, \n or `,`) (CP #2)
    |                   # Or
    ([^\r\n,])          # Match one-char string (CP #3)
)?                  # Optional - End of non-capturing group (b)

(?:                 # Start of non-capturing group (c) 
    (,$)                # Match `,$` (CP #4)
    |                   # Or
    (,)                 # Match single comma (CP #5)
    |                   # Or
    ($)                 # Assert end of line (CP #6)
)                   # End of non-capturing group (c)

edited Oct 09 '16 at 10:08

answered Oct 08 '16 at 23:06

revo

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2:30AM here I'm not fresh to add explanation. But I'll do asap. – revo Oct 08 '16 at 23:10
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+1 for being a one-step-solution, though I think a multi-step-solution is much more readable (and could be used as a macro) – Sebastian Proske Oct 08 '16 at 23:13
For the most part that works. And being one step, while confusing, is efficient. But it seems to fail if there is non-alphanumeric characters in the text. For instance, if `some-value` is in there, it stops at the `-` and moves on to the next line. Tried to work out how to modify it, but I'm not knowledgeable enough in regex to figure out how to do it. – MSCF Oct 09 '16 at 02:27
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@MSCF It's a matter of changing `\w` to `[^\r\n,]`. Please check update. – revo Oct 09 '16 at 10:09
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Works like a champ. And thank you for the explanation. I can see how it works now. I need to study up on regex. – MSCF Oct 09 '16 at 21:05

Sergey Kalinichenko · Answer 2 · 2016-10-09T00:58:49.773

1

The first replace adds | at the beginning and at the end, and replaces commas:

Search: ^|$|,
Replace: |

The second replace adds space around single character matches:

Search: (?<=[|])([^|])(?=[|])
Replace:   $1

Add spaces to the left and to the right of $1.

edited Oct 09 '16 at 00:58

answered Oct 08 '16 at 22:45

Sergey Kalinichenko

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Have you tested? The second one doesn't work, even if you escape the pipes. – Sebastian Proske Oct 08 '16 at 23:05
@SebastianProske I'm on my iPhone, so I can't test it at the moment. What's wrong with the expression? – Sergey Kalinichenko Oct 08 '16 at 23:09
`[|](.)[|]` will match on triple `|` and wont work on sequences of multiple single characters (as `|a|b|c|`) – Sebastian Proske Oct 08 '16 at 23:12
@SebastianProske Ah, you are right! Bars will consume the input, so I need to make them into look-arounds. – Sergey Kalinichenko Oct 08 '16 at 23:21
Guess you mixed up lookahead and lookbehind. Still problematic on `|||` – Sebastian Proske Oct 08 '16 at 23:27
Also your first regex doesn't meet the requirements fully, when there is a comma at the end of line. – revo Oct 08 '16 at 23:36

Sebastian Proske · Answer 3 · 2016-10-08T23:22:53.150

1

Three Step Solution:

Pattern: ^.+$ Replacement: |$0|
Pattern: , Replacement: |
Pattern: (?<=\|)([^|\r\n])(?=\|) Replacement: $0

edited Oct 08 '16 at 23:22

answered Oct 08 '16 at 22:47

Sebastian Proske

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Notepad++ regex to find single character bounded by |

3 Answers3