Awk throws "No such file or directory error" where using hostname -I

Question

This command works fine are print the hostname

awk -v MYHOST=$(hostname) '{printf(MYHOST)}'

However on running

awk -v MYHOST=$(hostname -I) '{printf(MYHOST)}'

throws a

awk: cannot open "ip address" (No such file or directory)

Answer 1

You should always use double-quotes around command substitutions. The following command is fixed, it will not throw the error:

awk -v MYHOST="$(hostname -I)" '{printf(MYHOST)}'

---

With $(hostname -I) unquoted, these are possible outcomes (after expansion):

• awk -v MYHOST= '{printf(MYHOST)}'
  

  This will formally work.

• awk -v MYHOST=1.2.3.4 '{printf(MYHOST)}'
  

  This will formally work.

• awk -v MYHOST=1.2.3.4 5.6.7.8 '{printf(MYHOST)}'
  

  This will treat 5.6.7.8 as a script and {printf(MYHOST)} as a file to be parsed. The error will be like cannot open '{printf(MYHOST)}' (No such file or directory), unless there is such file.

• awk -v MYHOST=1.2.3.4 5.6.7.8 9.10.11.12 … '{printf(MYHOST)}'
  

  where … indicates zero or more additional addresses. This will treat 5.6.7.8 as a script and 9.10.11.12 … '{printf(MYHOST)}' as multiple files to be parsed. The error will mention the first nonexistent "file", e.g. cannot open '9.10.11.12' (No such file or directory).

  This is what happened in your case.