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Incorrectly using 'ls' in if/then alias

 
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# 1  
Old 05-13-2013
Incorrectly using 'ls' in if/then alias
I have an alias defined in which I wish to print the contents of a specific directory using 'ls' based on the if/then condition. The if/then conditions are being correctly evaluated, and the 'ls <path>' result is correct (tested directly in a terminal) although for some reason it seems the 'ls <path>' command isn't be executed. The <path> contents are not displayed. The only "workaround" I've found is to allow the alias to change the directory, and then call 'ls <path>' outside of the if/then logic. The alias is defined as follows (syntactically equivalent example):

Code:
alias mydir  'if ($a == "abc" || $a == "def") then
                        ls /$a/disks/abc/ \
                else if ($a == "ghi" || $a == "jkl") \
                        ls /$a/disks/def/ \
                else \
                        echo "Unrecognized var $a" \
                endif'

Any idea why the contents of the directory are not being listed? Thanks in advance for any suggestions.

/edit: added code tags
# 2  
Old 05-13-2013
Quote:
Originally Posted by coldcoffeecup
I
Any idea why the contents of the directory are not being listed?
Yes: the shell evaluates its command line in consecutive distinct steps. When it expands aliases the phase where variables are expanded is already over. Therefore "$a" doesn't get expanded any more.

The solution to this is "eval", which restarts the commandline evaluation process. Read your shells documentation about "eval".

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
coldcoffeecup
# 3  
Old 05-14-2013
is it a unix shell script.. if it is then i think syntax for creating alias is

Code:
alias LS='ls -l'

and the if/ then syntax is also different.

Code:
if [ "$a" = "abc" ]; then

elif [ "$b" = "cde" ]; then

else

fi

---------- Post updated at 10:02 AM ---------- Previous update was at 09:54 AM ----------

just try this if it works

Code:
alias mydir='if [ "$a" = "abc" ] || [ "$a" = "def" ]; then
ls /$a/disks/abc/
elif [ "$a" = "ghi" ] || [ "$a" = "jkl" ]; then
ls /$a/disks/def/
else
echo "unrecognized var $a"
fi'

# 4  
Old 05-14-2013
... and a function would be easier anyway.
But the OP uses csh not sh!

---------- Post updated at 08:45 AM ---------- Previous update was at 12:20 AM ----------

csh cannot handle a multi-line string.
A csh alias needs a string.
if-then-else-endif needs multi-line.
So this cannot be done.
If you insist in using csh, your only option is to write an executable script.
Your original code, slightly adjusted:
Code:
#!/bin/csh -f
if ("$1" == "abc" || "$1" == "def") then
  ls /"$1"/disks/abc/
else if ("$1" == "ghi" || "$1" == "jkl") then
  ls /"$1"/disks/def/
else
  echo "Unrecognized var $1"
endif

Save this with name "mydir", make it executable with chmod 755 mydir,
and run it e.g. with ./mydir abc
# 5  
Old 05-14-2013
Quote:
Originally Posted by bakunin
The solution to this is "eval"
Worked simply/perfectly. Thanks!

And thank you everybody else who pitched in =)
 
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