Bash printf - using array as argument

Question

I'm trying to print out some data from my code as a debug tool in bash. So I want to store all data in an array were I later on print it out.

So far I have setup printf with some arguments:

DATA_ARRAY+=("\n%-5s %-10s %-15s %-10s %-5s %-5s %-5s %-120s" "data1" "data2" "data3" "data4" "data5" "data6" "data7" "data8") were data is a random text in this case. This will give me a nice column based text in the terminal.

However the other data may look somewhat simpler:

DATA_ARRAY+=("\n%-s" "[Remove] \ID: $dataID Data missing -> Removing $dataID")

My final line is to print all with printf

printf "${REMOVE_DATA_ARRAY[*]}".

So my problem now is that all the data will not keep the structure when I print it and it react to characters such as "s" and "i".

So my question is, is it possible to do this without escaping each character (s,i) and print the hole array with the given structure above.

I do not want to print each part at a time.

The program does work if I do

printf ("\n%-5s %-10s %-15s %-10s %-5s %-5s %-5s %-120s" "data1" "data2" "data3" "data4" "data5" "data6" "data7" "data8")

Directly but this is not what I want to do.

that other guy · Accepted Answer · 2019-09-10 22:24:37Z

2

"${array[*]}" will concatenate all elements into a single argument. "${array[@]}" will expand to one argument per element:

$ args=("Hello %s\n" "World")
$ printf "${args[@]}"
Hello World

answered Sep 10, 2019 at 22:24

that other guy

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5 Comments

David C. Rankin Over a year ago

Yep, that's the way to skin that cat.

Fredrik Over a year ago

Tried doing that but the arguments "\n%-5s %-10s %-15s %-10s %-5s %-5s %-5s %-120s" got included in the print instead of being an argument

that other guy Over a year ago

@Fredrik Only the first argument will be used as a format string. You append onto an array, so there are probably items in there already. You can check that with declare -p DATA_ARRAY

Fredrik Over a year ago

@thatotherguy So each new item I add into it will ignore the format I place and I can therefor only format an array once? If that is the case is it possible to work around this and add a second format in the middle of the array?

that other guy Over a year ago

There is no way to do printf "%s" Hello "%s\n" World, no. You can use multiple printfs though. Maybe instead of collecting multiple format strings and multiple arguments, you can do the printf right there and instead collect pre-formatted strings

markp-fuso · Accepted Answer · 2019-09-10 23:14:27Z

How about splitting the format string and data into 2 separate variables:

MYFMT : (simple variable) append successive format strings onto the end of this variable
DATA_ARRAY : (array) append successive items to the end of this array

Using the samples from the question we get:

$ MYFMT="\n%-5s %-10s %-15s %-10s %-5s %-5s %-5s %-120s"
$ DATA_ARRAY=("data1" "data2" "data3" "data4" "data5" "data6" "data7" "data8")

$ dataID=666

$ MYFMT="${MYFMT} \n%s"
$ DATA_ARRAY+=("[Remove] \ID: $dataID Data missing -> Removing $dataID")

$ printf "${FMT}" "${DATA[@]}"
data1 data2      data3           data4      data5 data6 data7 data8

[Remove] \ID: 666 Data missing -> Removing 666

# to see what printf sees:

$ set -x

$ printf "${FMT}" "${DATA[@]}"
+ printf '\n%-5s %-10s %-15s %-10s %-5s %-5s %-5s %-120s \n%s' data1 data2 data3 data4 data5 data6 data7 data8 '[Remove] \ID: 666 Data missing -> Removing 666'

data1 data2      data3           data4      data5 data6 data7 data8

[Remove] \ID: 666 Data missing -> Removing 666

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