Bash - saving string to separate variable after custom delimiter

Question

I'm fairly new to Bash so please forgive me, but I'm building a Bash script that can accept a user input command that can have a lot of switches. I need to write a function that pulls specific data from that user provided command.

I can't seem to find a way to pull each word after "-mode" and push it into an array or list of some sort.

Here is an example of what the user input command might look like:

/home/custom/function/that/accepts/a/billion/switches  random_info random_info2 -worker vendor_schmo  -switch_one  -anotherOne  -more_switches  -optionTwo        -mode FOO -mode BAR -mode BAZ -mode BAG -mode DAT -mode RAR

I've tried fiddling with awk -F "-mode" '{ print $1 }' and that didn't work. Any advice would be much appreciated!!

Here is the snippet from the script that pulls this info:

manualRunMain(){
  local command
  manualRunHeaderPrint
  echo
  echo
  echo
  echo
  lineBreakPrint
  read -p "Enter your command here: " command
  sleep .25
  manualRun "$command"
}

manualRun(){
  manualRunHeaderPrint
  jobRunSubHeaderPrint
  pullModeNames "$1"
}

pullModeNames(){

}

Welcome to stack overflow, could you please add sample expected output in code tags too? — RavinderSingh13
– RavinderSingh13, Commented Aug 14, 2017 at 18:15
I don't think I need anything output, I just need to push each word after each "-mode" into an array. I think that would be enough and I could take it from there. — johnathon doeth
– johnathon doeth, Commented Aug 14, 2017 at 18:20
In general, you should consider following the practices given in BashFAQ #35 for your given purpose. The list of arguments your command is given is not passed as a string -- rather, it's passed as an array of strings -- and treating it as if a string means you adopt a bunch of bugs (for instance, you lose the ability to distinguish between -foo "bar baz" and -foo bar baz). — Charles Duffy
– Charles Duffy, Commented Aug 14, 2017 at 19:16
(and if you have a string and need to split it into a list of strings in a way that's comparable to what the shell would do, such that that array can then be parsed through using standard tools, that's a fairly involved question in its own right, with an answer that's much more complicated than array=( $string ); that said, it is a question with accepted, canonical answers already present in our knowledge base). — Charles Duffy
– Charles Duffy, Commented Aug 14, 2017 at 19:47

anubhava · Accepted Answer · 2017-08-14 18:50:46Z

2

You can use RS variable in awk to tell to split data into separate records when it get -mode:

s='/home/custom/function/that/accepts/a/billion/switches  random_info random_info2 -worker vendor_schmo  -switch_one  -anotherOne  -more_switches  -optionTwo        -mode FOO -mode BAR -mode BAZ -mode BAG -mode DAT -mode RAR'

printf '%s' "$s" | awk -v RS="-mode[[:space:]]*" 'NR>1'
FOO
BAR
BAZ
BAG
DAT
RAR

To populate an array:

mapfile -t arr < <(printf '%s' "$s" | awk -v RS="-mode[[:space:]]*" 'NR>1')

# examine array content
declare -p arr
declare -a arr=([0]="FOO" [1]="BAR" [2]="BAZ" [3]="BAG" [4]="DAT" [5]="RAR")

edited Aug 14, 2017 at 18:50

answered Aug 14, 2017 at 18:24

anubhava

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6 Comments

johnathon doeth Over a year ago

Thanks! This is perfect. I'd upvote you but I don't have reputation to do it yet :)

Benjamin W. Over a year ago

Notice that the command to populate an array is subject to word splitting and glob expansion, so if you have an argument -mode 'has space', it will break. Instead, you could use mapfile: mapfile -t arr < <(awk -v RS="-mode" 'NR>1{ print $1 }' <<< "$s")

anubhava Over a year ago

@BenjaminW.: Very good point, however if there is any whitespace then even print $1 will print only first part.

Benjamin W. Over a year ago

Since you're using RS, can't you print $0 in the first place? Might have to adjust RS to swallow whitespace. Something like RS="-mode *".

Charles Duffy Over a year ago

BTW, I agree that this is the best answer to the question asked in the title, but the intended use case given in the question text (command-line parsing) gives me qualms about this answer's fitness to purpose.

|

glenn jackman · Accepted Answer · 2017-08-14 19:11:11Z

0

I just came up with basically the same answer as @anubhava but with GNU grep instead of awk:

$ cmd="... -more_switches  -mode FOO BAR -mode BAZ -mode BAG -mode CAT DAT HAT -mode RAR"
$ mapfile -t modes < <(grep -oP -- '-mode \K.+?(?= -mode|$)' <<<"$cmd")
$ printf "%s\n" "${modes[@]}"
FOO BAR
BAZ
BAG
CAT DAT HAT
RAR

answered Aug 14, 2017 at 19:11

glenn jackman

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