Is it possible to put more than 1 condition in an if statement?
if [ "$name" != "$blank" && "$age" == "$blank" ]; then
Is it possible? If not how am I supposed to do that?
Asked
Active
Viewed 7,408 times
4
-
also has an answer [here](http://stackoverflow.com/questions/16203088/multiple-conditions-if-statement-bash-script) – Aman Jan 11 '15 at 12:45
2 Answers
9
With [ expression ] (POSIX Standard) syntax you can use the following:
if [ "$name" != "$blank" ] && [ "$age" = "$blank" ]; then
echo true
fi
But in [[ expression ]] syntax you can use both conditions:
if [[ $name != "$blank" && $age == "$blank" ]]; then
echo true!
fi
Two advantages of [[ over [:
- No word splitting or glob expansion will be done for
[[, and therefore many arguments need not be quoted (with the exception of the right-hand side of==and!=, which is interpreted as a pattern if it isn't quoted). [[easier to use and less error-prone.
Downside of [[: it is only supported in ksh, bash and zsh, not in plain Bourne/POSIX sh.
My reference and good page to comparing [[ and [: bash FAQ
Security implications of forgetting to quote a variable in bash/POSIX shells
Sepahrad Salour
- 2,629
- 3
- 20
- 27
-
-
You mention that [ is POSIX standard. It's worth pointing out that [[ isn't. But if you're using other BASH features anyway, then def. use [[, it's better. (e.g. the bash-completion project coding standards mandate use of [[ ]].) – Peter Cordes Jan 11 '15 at 13:28
4
Yet another possibility not mentioned by @SepahradSalour is to use -a operator:
if [ "$name" != "$blank" -a "$age" = "$blank" ]; then
BTW, be sure to quote properly all variables separately.
-
1[According to spec](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/test.html) *The XSI extensions specifying the -a and -o binary primaries and the '(' and ')' operators have been marked obsolescent. (Many expressions using them are ambiguously defined by the grammar depending on the specific expressions being evaluated.)* – mikeserv Jan 11 '15 at 12:53
-
-