511 ~$who | awk '/^'"$USER"'/' wang tty7 2009-12-23 09:00 (:0) wang pts/0 2009-12-23 09:00 (:0) 511 ~$who| awk '/^'"$USER"'/' wang tty7 2009-12-23 09:00 (:0) wang pts/0 2009-12-23 09:00 (:0) 较新版本的awk可以这样：
nawk 'END { print "Your path variable is " ENVIRON["PATH"] }' #如下： ~$awk --version GNU Awk 3.1.6 ~$export b=2; ~$awk 'END { print "Your path variable is " ENVIRON["b"] }' /dev/null Your path variable is 2 参考文章
3.12) Is it possible to pass shell variable settings into an awk program? There are two different ways to do this. The first involves simply expanding the variable where it is needed in the program. For example, to get a list of all ttys you’re using: who | awk ‘/^’"$USER"’/ { print $2 }’ (1) Single quotes are usually used to enclose awk programs because the character ‘$’ is often used in them, and ‘$’ will be interpreted by the shell if enclosed inside double quotes, but not if enclosed inside single quotes. In this case, we want the ‘$’ in “$USER” to be interpreted by the shell, so we close the single quotes and then put the “$USER” inside double quotes. Note that there are no spaces in any of that, so the shell will see it all as one argument. Note, further, that the double quotes probably aren’t necessary in this particular case (i.e. we could have done who | awk ‘/^’$USER’/ { print $2 }’ (2) ), but they should be included nevertheless because they are necessary when the shell variable in question contains special characters or spaces. The second way to pass variable settings into awk is to use an often undocumented feature of awk which allows variable settings to be specified as “fake file names” on the command line. For example: who | awk ‘$1 == user { print $2 }’ user="$USER" - (3) Variable settings take effect when they are encountered on the command line, so, for example, you could instruct awk on how to behave for different files using this technique. For example: awk ‘{ program that depends on s }’ s=1 file1 s=0 file2 (4) Note that some versions of awk will cause variable settings encountered before any real filenames to take effect before the BEGIN block is executed, but some won’t so neither way should be relied upon. Note, further, that when you specify a variable setting, awk won’t automatically read from stdin if no real files are specified, so you need to add a “-” argument to the end of your command, as I did at (3) above. A third option is to use a newer version of awk (nawk), which allows direct access to environment vairables. Eg. nawk ‘END { print “Your path variable is " ENVIRON[“PATH”] }’ /dev/null
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