Store two filenames into a variable which can be easily accessed by index 0 and 1

Question

I have two filenames that I would like to store in a Bash variable :

For this, I did :

$ b=$(ls Fisher_GCph_WL_XSAF_COLUMN*PESS_F*gamma_*)

I get the variable b equal to :

$ echo $b
Fisher_GCph_WL_XSAF_COLUMN2_2_PESS_F_FoM_33.22_gamma_0.071.txt
Fisher_GCph_WL_XSAF_COLUMN2_2_PESS_F_FoM_71.91_gamma_N.txt

I want to build an array of 2 elements containing the 2 filenames above.

I tried to access them by :

$d eclare -a b
$ echo ${b[0]}

returns nothing

and

$ echo ${b[1]} returns F

What to do to have an array of string where I could access directly to first or second filename by index 0 or 1 ?

Do the answers to ["Reading filenames into an array"](https://stackoverflow.com/questions/10981439/reading-filenames-into-an-array) cover your question? (Also, what shell are you using? What you describe does not match bash's normal behavior.) — Gordon Davisson, Jan 09 '22 at 21:12
You don't need `ls` here. The glob itself generates the two file names, which is why `ls` receives them as arguments. — chepner, Jan 10 '22 at 20:23

score 3 · Accepted Answer · answered Jan 09 '22 at 21:15

3

You just need a simple array assignment and globbing.

shopt -s nullglob
b=(Fisher_GCph_WL_XSAF_COLUMN*PESS_F*gamma_*)

answered Jan 09 '22 at 21:15

konsolebox

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Just to add about `shopt -s nullglob`: depending on the context, saving + restoring `nullglob` might be a good idea – Fravadona Jan 09 '22 at 23:28

score 1 · Answer 2 · answered Jan 09 '22 at 22:03

The index notation you use is correct. The issue here b is not an array but a multiline string.

To declare a true array:

b=("Fisher_GCph_WL_XSAF_COLUMN2_2_PESS_F_FoM_33.22_gamma_0.071.txt" "Fisher_GCph_WL_XSAF_COLUMN2_2_PESS_F_FoM_71.91_gamma_N.txt")

NOTE - no comma between elements

bash treats b as an array:

declare -a b='([0]="Fisher_GCph_WL_XSAF_COLUMN2_2_PESS_F_FoM_33.22_gamma_0.071.txt" [1]="Fisher_GCph_WL_XSAF_COLUMN2_2_PESS_F_FoM_71.91_gamma_N.txt")'

Compare that to return from ls:

$ c=$(ls)
$ declare -p c
declare -- c="Fisher_GCph_WL_XSAF_COLUMN2_2_PESS_F_FoM_33.22_gamma_0.071.txt
Fisher_GCph_WL_XSAF_COLUMN2_2_PESS_F_FoM_71.91_gamma_N.txt"

In your case I would

Create an intermediate file:

ls -1 > filelist

This is 'one' not 'l' - one row per file

Convert file into array:

$mapfile -t b < filelist

Validate b is an array:

$ declare -p b

Use the array:

echo  ${b[1]}

Store two filenames into a variable which can be easily accessed by index 0 and 1

2 Answers2