How can I extract digits at the end of a string in UNIX shell scripting? Post: 303026270

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Top Forums Shell Programming and Scripting How can I extract digits at the end of a string in UNIX shell scripting? Post 303026270 by bakunin on Friday 23rd of November 2018 04:34:12 AM

11-23-2018

Registered User

Quote:

Originally Posted by mingch

I tried to create the following scripts but it can't increment the last number from 012 to 013, anyone help? Many thanks.

The reason is that "012" is not a number. "12" is a number and you can increment that to "13". But "012" and "013" are strings and you cannot do calculations with strings.

You haven't told us yet what your shell is and in fact it didn't matter that much because what we did up to now was common ground to all of them. We are leaving this area and maybe i will tell you something you can't use because you have a different shell - which is why you should always state what your environment (OS and shell and their versions most prominently) is.

In Korn shell (ksh) you can use typeset to make a variable have leading zeroes and having a certain length like this (try it on the command line):

Code:

$ typeset -RZ3 variable=12
$ echo $variable
012
$ (( variable += 1 ))
$ echo $variable
013

Variables in shell do not really have a certain "type". Of course it will lead to an error if you try to multiply "abc" by 3 but if you create a string "ab12cd", then somehow (you now know how) get rid of the characters you can multiply the remaining "12" and it will give you "60", which you still can use as a string. What we did above was to create a string, right-aligned (-R) in the length of 3 where every "free"space is filled with zeroes. When we calculate with it like a number, the shell will silently drop the leading zeroes to make the number "12" from "012", then do the calculation and, when writing the result back, realign and refill it (because of the typeset directive, so that "013" is the final content.

I hope this helps.

bakunin

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LEARN ABOUT REDHAT

mac2unix

dos2unix(1)						      General Commands Manual						       dos2unix(1)

NAME

       dos2unix - DOS/MAC to UNIX text file format converter

SYNOPSYS

       dos2unix [options] [-c convmode] [-o file ...] [-n infile outfile ...]

       Options:

       [-hkqV] [--help] [--keepdate] [--quiet] [--version]

DESCRIPTION

       This manual page documents dos2unix, the program that converts plain text files in DOS/MAC format to UNIX format.

OPTIONS

       The following options are available:

       -h --help
	      Print online help.

       -k --keepdate
	      Keep the date stamp of output file same as input file.

       -q --quiet
	      Quiet mode. Suppress all warning and messages.

       -V --version
	      Prints version information.

       -c --convmode convmode
	      Sets conversion mode. Simulates dos2unix under SunOS.

       -o --oldfile file ...
	      Old file mode. Convert the file and write output to it. The program default to run in this mode. Wildcard names may be used.

       -n --newfile infile outfile ...
	      New  file  mode.	Convert the infile and write output to outfile. File names must be given in pairs and wildcard names should NOT be
	      used or you WILL lost your files.

EXAMPLES

       Get input from stdin and write output to stdout.

	      dos2unix

       Convert and replace a.txt. Convert and replace b.txt.

	      dos2unix a.txt b.txt

	      dos2unix -o a.txt b.txt

       Convert and replace a.txt in ASCII conversion mode.  Convert and replace b.txt in ISO conversion mode.  Convert	c.txt  from  Mac  to  Unix
       ascii format.

	      dos2unix a.txt -c iso b.txt

	      dos2unix -c ascii a.txt -c iso b.txt

	      dos2unix -c mac a.txt b.txt

       Convert and replace a.txt while keeping original date stamp.

	      dos2unix -k a.txt

	      dos2unix -k -o a.txt

       Convert a.txt and write to e.txt.

	      dos2unix -n a.txt e.txt

       Convert a.txt and write to e.txt, keep date stamp of e.txt same as a.txt.

	      dos2unix -k -n a.txt e.txt

       Convert and replace a.txt. Convert b.txt and write to e.txt.

	      dos2unix a.txt -n b.txt e.txt

	      dos2unix -o a.txt -n b.txt e.txt

       Convert c.txt and write to e.txt. Convert and replace a.txt.  Convert and replace b.txt. Convert d.txt and write to f.txt.

	      dos2unix -n c.txt e.txt -o a.txt b.txt -n d.txt f.txt

DIAGNOSTICS

BUGS

       The program does not work properly under MSDOS in stdio processing mode.  If you know why is that so, please tell me.

AUTHORS

       Benjamin Lin - <blin@socs.uts.edu.au>

       Bernd Johannes Wuebben (mac2unix mode) <wuebben@kde.org>

MISCELLANY

       Tested environment:

	      Linux 1.2.0 with GNU C 2.5.8

	      SunOS 4.1.3 with GNU C 2.6.3

	      MS-DOS 6.20 with Borland C++ 4.02

       Suggestions and bug reports are welcome.

SEE ALSO

       unix2dos(1) mac2unix(1)

1995.03.31							   dos2unix v3.0						       dos2unix(1)

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