parsing a string
I'm new to bash and am trying to write a script that puts 3 substrings in 3 variables. I have a string with password,firstname,lastname. and I need it to be in 3 variables. I bought a bash scripting book but I can't seem to make it work. Thanks in advance.
Dave
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Quoted 3 lines · [email protected] wrote:
I'm new to bash and am trying to write a script that puts 3 substrings in 3 variables. I have a string with password,firstname,lastname. and I need it to be in 3 variables.
I'm just an apprentice here, but I think "cut" is a good choice of tool.
$ echo 'password,firstname,lastname' | cut -d',' -f1 password $ echo 'password,firstname,lastname' | cut -d',' -f2 firstname $ echo 'password,firstname,lastname' | cut -d',' -f3 lastname
-d is the field delimiter, -f says which fields you want
John
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Quoted 7 lines · John Aspinall
Quoted 3 lines · [email protected] wrote:
I'm new to bash and am trying to write a script that puts 3 substrings in 3 variables. I have a string with password,firstname,lastname. and I need it to be in 3 variables.
I'm just an apprentice here, but I think "cut" is a good choice of tool.
Quoted 8 lines
$ echo 'password,firstname,lastname' | cut -d',' -f1 password $ echo 'password,firstname,lastname' | cut -d',' -f2 firstname $ echo 'password,firstname,lastname' | cut -d',' -f3 lastname-d is the field delimiter, -f says which fields you want
I agree that "cut" is a wonderful tool on the command line. However, a more purely bash solution is to use a powerful feature of variable expansion in bash. For example:
pass_first_last='password,firstname,lastname'
pass=${pass_first_last%%,*}
first_last=${pass_first_last#*,}
first=${first_last%,*}
last=${first_last#*,}
or, alternatively,
last=${pass_first_last##*,}
The "#" operator in variable expansion takes a pattern argument and removes as little as possible from the left side of the variable value that matches the pattern. The "##" operator in variable expansion takes a pattern argument and removes as much as possible from the left side of the variable value that matches the pattern. The "%" operator in variable expansion takes a pattern argument and removes as little as possible from the right side of the variable value that matches the pattern. The "%%" operator in variable expansion takes a pattern argument and removes as much as possible from the right side of the variable value that matches the pattern.
A common use for this is to extract the final filename from a pathname:
filename=${pathname##*/}
Another is to extract the directory path name from a file's path:
dirname=${pathname%/*}
P.S. I was trying to use cut to extract one field from a file using FS (\0x1C) as the field delimiter. I discovered it was non-trivial to get the FS into my cut command. The solution turned out to be a "string expansion" in bash:
cut -d$'\x1C' -f2 filename
--
Jeff Woods <[email protected]>
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