Inline If Shell Script

Inline if shell script

It doesn't work because you missed out fi to end your if statement.

counter=`ps -ef | grep -c "myApplication"`; if [ $counter -eq 1 ]; then echo "true"; fi

You can shorten it further using:

if [ $(ps -ef | grep -c "myApplication") -eq 1 ]; then echo "true"; fi

Also, do take note the issue of ps -ef | grep ... matching itself as mentioned in @DigitalRoss' answer.

update

In fact, you can do one better by using pgrep:

if [ $(pgrep -c "myApplication") -eq 1 ]; then echo "true"; fi

One line if/else condition in linux shell scripting

It looks as if you were on the right track. You just need to add the else statement after the ";" following the "then" statement. Also I would split the first line from the second line with a semicolon instead of joining it with "&&".

maxline='cat journald.conf | grep "#SystemMaxUse="'; if [ $maxline == "#SystemMaxUse=" ]; then sed 's/\#SystemMaxUse=/SystemMaxUse=50M/g' journald.conf > journald.conf2 && mv journald.conf2 journald.conf; else echo "This file has been edited. You'll need to do it manually."; fi

Also in your original script, when declaring maxline you used back-ticks "`" instead of single quotes "'" which might cause problems.

Is there an inline-if with assignment (ternary conditional) in bash?

There is no ?: conditional operator in the shell, but you could make the code a little less redundant like this:

if [ $useDefault ]; then
    tmpname="$defaultName"
else
    tmpname="$customName"
fi
fileName="$dirName/$tmpname.txt"

Or you could write your own shell function that acts like the ?: operator:

cond() {
    if [ "$1" ] ; then
        echo "$2"
    else
        echo "$3"
    fi
}

fileName="$dirname/$(cond "$useDefault" "$defaultName" "$customName").txt"

though that's probably overkill (and it evaluates all three arguments).

Thanks to Gordon Davisson for pointing out in comments that quotes nest within $(...).

How to write if else in one line in shell?

Space -- the final frontier. This works:

if [ $SERVICESTATEID -eq 2 ]; then echo "CRITICAL"; else echo "OK"; fi

Note spaces after [ and before ] -- [ is a command name! And I removed an extra $ at the end of $SERVICESTATEID.

An alternative is to spell out test. Then you don't need the final ], which is what I prefer:

if test $SERVICESTATEID -eq 2; then echo "CRITICAL"; else echo "OK"; fi

Bash: If/Else statement in one line

There is no need to explicitly check $?. Just do:

ps aux | grep some_proces[s] > /tmp/test.txt && echo 1 || echo 0 

Note that this relies on echo not failing, which is certainly not guaranteed. A more reliable way to write this is:

if ps aux | grep some_proces[s] > /tmp/test.txt; then echo 1; else echo 0; fi

Capture and check return status inline in if statement inside [[ ]]

This does not make sense:

if cmd ; ...

would run cmd and then branch depending on the exit status of cmd.

Similarily,

if [[ cmd ]]; ....

runs the command [[...]] and branch accordingly. It does not run cmd.

Actually, as long as you are only interested in knowing whether the exit status is zero or not, I see no reason why you should fiddle around with $?. Things are different if you have several exit status values to distinguish. For example:

grep foo bar; status=$?
if (( status == 0 ))
then
   # actions where grep found the pattern
elif (( status == 1 ))
   # actions where grep did not find the pattern
else
   # actions where grep encountered a serious problem
fi

In this case, store the exit code immediately after invoking your command into some variable, and process it later with if or case or whatever you need.

Ternary operator (?:) in Bash

ternary operator ? : is just short form of if/else

case "$b" in
 5) a=$c ;;
 *) a=$d ;;
esac

Or

 [[ $b = 5 ]] && a="$c" || a="$d"

---

Related Topics