that's what I figured. I'm trying to rationalize this syntax...
if [ not and file ] then....
I'm not comprehending the logic here, it's checking for ! (not) what. and checking for file. So where does it say to check the pwd for that file name. What value does ! by itself give back.
Therefore the test succeeds when the file does not exist.
Fun If Fact
Quote:
At times you need to specify different courses of action to be taken in a shell script, depending on the success or failure of a command. The if construction allows you to specify such conditions.
The most compact syntax of the if command is:
if TEST-COMMANDS; then CONSEQUENT-COMMANDS; fi
The TEST-COMMAND list is executed, and if its return status is zero, the CONSEQUENT-COMMANDS list is executed. The return status is the exit status of the last command executed, or zero if no condition tested true.
The TEST-COMMAND often involves numerical or string comparison tests, but it can also be any command that returns a status of zero when it succeeds and some other status when it fails. Unary expressions are often used to examine the status of a file. If the FILE argument to one of the primaries is of the form /dev/fd/N, then file descriptor "N" is checked. stdin, stdout and stderr and their respective file descriptors may also be used for tests.
My "man test" does not have a "-a" option, but that may depend on my OS. The "man test" on my system says you can test this (and much more):
-e file exists
! -e file doesn't exist
-s file exists and has a size greater than zero
! -s file doesn't exist and/or has a size of zero
You can test many, many situations and this is very handy.
Sometimes you would like to know if a file exists, like so: if [ -e filename ] or if a file does not exist, like so: if [ ! -e filename ].
You could write an if-statement to check if a file exists and give an error if it doesn't, like so:
Code:
if [ -e filename ]; then
echo "It's here and I don't want to do anything, because I only want to know if it's NOT here"
else
echo "File's not here!"
fi
But checking for the "not-existance" is sometimes much more efficient, because you might not care about the other situation:
Code:
if [ ! -e filename ]; then
echo "ERROR! File's not here!"
fi
It all depends on the function of your if-statement.
Hi,
I installed some packages required by an app built with python.
But when I try python setup.py install, I get the following error:
/opt/csw/lib/gcc/sparc-sun-solaris2.10/5.2.0/../../../../sparc-sun-solaris2.10/bin/as: unrecognized option `-m32'
Could anyone tell me what's wrong... (4 Replies)
Hi folks,
I have a scenario to convert the update statements into insert statements using shell script (awk, sed...) or in database using regex.
I have a bunch of update statements with all columns in a file which I need to convert into insert statements.
UPDATE TABLE_A SET COL1=1 WHERE... (0 Replies)
I working on my Apache2 restore script.
This is the code so far
updatedb
prompt_list "Whick configuration_backup file do you want to use?" `find /restore/configuration/ -name configuration_backup* -type d`
BACKUP_OBJECT=${CHOICE}
echo "--------------------------------------"
cd... (10 Replies)
Hi Guys,
I'm sorry but I can't find answer for this, what is the meaning of -s option in "if" statement on unix scipting. Please see sample below:
opath=/home/output
for i in N1 N2 N3 N4
do
echo $i
if
then
grep $i $opath/N5_CRAI > $opath/N5_$i.crai
chmod 777 $opath/N5_$i.crai
... (7 Replies)
To find all the files in your home directory that have been edited in some way since the last tar file, use this command:
find . -newer backup.tar.gz
Is anyone familiar with an older solution?
looking to identify files older then 15mins across several directories.
thanks,
manny (2 Replies)
Hi All,
I am using Unix ksh script.
I need to insert values to a table using the o/p from a slelect statement.
Can anybody Help!
My script looks like tihs.
---`sqlplus -s username/password@SID << EOF
set heading off
set feedback off
set pages 0
insert into ${TB_NAME}_D... (2 Replies)
In my ksh script, if the conditions of a if statement are true, then do nothing; otherwise, execute some commands.
How do I write the "do nothing" statement in the following example?
Example:
if (( "$x"="1" && "$y"="a" && "$z"="happy" ))
then
do nothing
else
command
command
fi... (3 Replies)
hi everybody, can somebody tell me what -R option on g++ on solaris means :
g++ -DAIX -fpic -static -o printps printps.o -L/epost2/blitz/xercesc1_1 /lib -L/oracle/OraHome/lib32/ L/epost2/blitz/lib -lxerces-c1_1 -lhmltods -lhmlt ops -lgeneric -lnotify -lutil -lclntsh `cat... (0 Replies)
Hi all,
I am parsing command line options using getopts.
The problem is that mandatory argument options following ":" is taking next option as argument if it is not followed by any argument.
Below is the script:
while getopts :hd:t:s:l:p:f: opt
do
case "$opt" in
-h|-\?)... (2 Replies)
my yacc output file y.tab.c is not compiling using cc y.tab.c -ly command
.possibily option flag -ly is not correct.i m using red hat linux 9.please give solutions. (4 Replies)
