How to set the From email address for mailx command?
You can use the “-r” option to set the sender address: mailx -r me@example.com -s …
shell
Why & How fish does not support POSIX?
fish isn’t and never tried to be compatible with POSIX sh. This really just means that it’s a separate language (like Java, Python or Ruby) rather than an implementation or extension of sh (like Bash, Dash and Ksh). Obviously, just like you can’t copy-paste Java snippets into a Python program, you can’t copy-paste sh code … Read more
if statement to check $HOSTNAME in shell script
The POSIX and portable way to compare strings in the shell is if [ “$HOSTNAME” = foo ]; then printf ‘%s\n’ “on the right host” else printf ‘%s\n’ “uh-oh, not on foo” fi A case statement may be more flexible, though: case $HOSTNAME in (foo) echo “Woohoo, we’re on foo!”;; (bar) echo “Oops, bar? Are … Read more
get last line from grep search on multiple files
for f in $(find . -name “FILE_NAME”); do grep PATTERN $f | tail -1; done
Is there a static analysis tool like Lint or Perl::Critic for shell scripts?
I found shellcheck: it tests for common errors in quoting and other things you overlook (“because it works”).
How to store an output of shell script to a variable in Unix?
Two simple examples to capture output the pwd command: $ b=$(pwd) $ echo $b /home/user1 or $ a=`pwd` $ echo $a /home/user1 The first way is preferred. Note that there can’t be any spaces after the = for this to work. Example using a short script: #!/bin/bash echo “hi there” then: $ ./so.sh hi there … Read more
Have Find print just the filenames, not full paths
If you’re using GNU find, then find path -printf “%f\n” will just print the file name and exclude the path.
How to replace one character with two characters using tr
No, tr is specifically intended to replace single characters by single characters (or, depending on command-line options, to delete characters or replace runs of a single character by one occurrence.). sed is probably the best tool for this particular job: $ echo “asdlksad ~ adlkajsd ~ 12345” | sed ‘s/~/~\n/g’ asdlksad ~ adlkajsd ~ 12345 … Read more
Escape backquote in a double-quoted string in shell
You need to escape the backtick, but also escape the backslash: $ touch 1\` $ /bin/sh -c “ls 1\\\`” 1` The reason you have to escape it “twice” is because you’re entering this command in an environment (such as a shell script) that interprets the double-quoted string once. It then gets interpreted again by the … Read more