Run a concatenated string as a command within a Bash script [duplicate]

Question

I'm trying to count the number of files with different extensions in /foo/. case 1 works as expected, but more flexible situations such as case 2 or case 3 don't work as expected.

File test.sh

# case 1
vista=$(find /foo/*.zip -atime -1)
echo "$vista" | wc -l

# case 2
vista=$(find /foo/*)

echo "$vista.zip -atime -1" | wc -l

# case 3
echo "$vista.xz -atime -1" | wc -l

Output:

./test.sh 
187
4566
4566

I suspect the problem is that for example echo "$vista.zip -atime -1" from case 2 runs first find /foo/* before appending the string zip -atime -1, but I don't know how to do it right.

See Is it OK for users to edit the accepted answer into the question?. For a Community Wiki answer (which isn't owned by any individual but open for anyone to edit with no individual getting rep points / credit), feel free to add your refinements to that answer itself. — Charles Duffy
– Charles Duffy, Commented Apr 24, 2019 at 17:04
Following @Charles Duffy's advise, a solution with functions is: find_under_foo() { find /foo/*"$1" "${@:2}"; } find_under_foo zip -atime -1 | wc -l — user3889486
– user3889486, Commented Apr 24, 2019 at 17:24
Also, vista=$(find /foo/*) doesn't do anything like storing a command in the variable, it runs the command and stores its output in the variable. So it might set vista to something like "/foo/file1\n/foo/file2" (where the \n represents an actual newline character). Then echo "$vista.zip -atime -1" | wc -l expands to echo "/foo/file1\n/foo/file2.zip -atime -1" | wc -l which isn't even slightly close to what you want. — Gordon Davisson
– Gordon Davisson, Commented Apr 24, 2019 at 20:14

2 revs · Accepted Answer · 2019-04-24 16:33:06Z

1

Code should never be stored in strings (unless using printf %q to generate eval-safe versions of variables, and then using eval at runtime). Use either an array (for dynamically-constructed content) or a function.

The former:

find_cmd=( find /foo/* )
"${find_cmd[@]}" -atime -1 | wc -l

The latter:

find_under_foo() { find /foo/* "$@"; }
find_under_foo -atime -1 | wc -l

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