bash debug – log all executed commands

2014-02-03 1 min read Bash

Whenever I am writing a script in perl or bash, I always wish that there
was some way to have all the commands logged or output to screen. I know
there is “set -x” option to have debugging enabled, but sometimes that
seems to be too much information and I dont really need all that. So, here
is something I found recently for bash to log all the executed commands.

Print all environment variables, including hidden ones

2010-11-09 2 min read Bash Fedora Linux

Print all environment variables, including hidden ones

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      for _a in {A..Z} {a..z};do _z=${!${_a}*};for _i in `eval echo "${_z}"`;do echo -e "$_i: ${!_i}";done;done|cat -Tsv
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This uses some tricks I found while reading the bash man page to enumerate and display all the current environment variables, including those not listed by the ‘env‘ command which according to the bash docs are more for internal use by BASH. The main trick is the way bash will list all environment variable names when performing expansion on ${!A*}. Then the eval builtin makes it work in a loop.

Verify all the paths in the PATH directory

2010-06-08 1 min read Bash Learning Linux

Here is the command to test that all the directories in your path actually exist.

(<a class="zem_slink freebase/en/internal_field_separator" title="Internal field separator" rel="wikipedia" href="http://en.wikipedia.org/wiki/Internal_field_separator">IFS=:;for p in $PATH; do test -d $p || echo $p; done)

And the explanation :

Set the IFS to ”:”

now we loop through the PATH variable

and test all the directories with ”test -d”

Here is another version without IFS:

for i in ${PATH//:/ };do test -d $i || echo $i;done
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