In one bash script i found the next construction:
if [[ "${xvar[id]:0:${#cnt}}" != "$cnt" ]]; then
Can someone explain what the above condition does?
In one bash script i found the next construction: if [[ ${xvar[id]:0:${#cnt}} != $cnt
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In one bash script i found the next construction:
if [[ "${xvar[id]:0:${#cnt}}" != "$cnt" ]]; then
Can someone explain what the above condition does?
The complicated expression is:
${xvar[id]:0:${#cnt}}.$xvarmust be an array, possibly associative. If it is associative, the part${xvar[id]}refers to the element of the array identified by the string ‘id’; if not, then it refers to the element indexed by variable$id(you’re allowed to omit the nested$), as noted by chepner in a comment.The
${xxx:0:${#cnt}}part of the expression refers to a substring from offset 0 to the length of the variable$cnt(so${#cnt}is the length of the string in the variable$cnt).All in all, the test checks whether the first characters of
${xvar[id]}are the same as the value of$cnt, so is the value in$cnta prefix of the value in${xvar[id]}.