Bash Syntax for Using GREP to Extract Text from File and Store in an Array

Question

I have recently upgraded from bash 4.2.46 to bash version 4.2.50

I had a script with the line:

mapfile -t my_array < <(grep ${ID} -w /etc/passwd | cut -d ":" -f 1,4,5)

where ID is an arbitrary integer we'd like to look for in the file passwd and then load all results into an array.

that used to work but now throws an error

usage: grep [-r] [-R] [-H] [-L] [-E|-F] [-c|-l|-q] [-insvxbhwyu] [-p[parasep]] -e pattern_list...
        [-f pattern_file...] [file...]
usage: grep [-E|-F] [-c|-l|-q] [-insvxbhwyu] [-p[parasep]] [-e pattern_list...]
        -f pattern_file... [file...]

can anyone explain how to work around this depreciation? I have attempted using sed and awk however the issue seems to be the format of my output redirection.

the text file passwd looks like this name:garbageData:garbageData:ID:password

Answer 1

You would get that error if you executed the script with ksh instead of with bash; either the sh-bang header line incorrectly points to ksh, or it points to /bin/sh which is ksh on AIX, or you're explicitly calling it as ksh /the/script.

ksh does not support mapfile nor with versions prior to ksh93t+, the <( ...) process substitution syntax when used as the target of a redirection, such as <. Clarification provided by Stéphane Chazelas.

Fix the sh-bang line to call bash (or explicitly invoke bash instead of ksh, if that's the case).

Additionally, the grep command is complaining because you've put an argument before all of the options; rearrange the grep to be:

grep -w "${ID}" /etc/passwd

(also quoting the variable expansion).