There are many different ways that an conditional statement can be used. These are summarized here:
| String Comparison | Description |
|---|---|
| Str1 = Str2 | Returns true if the strings are equal |
| Str1 != Str2 | Returns true if the strings are not equal |
| -n Str1 | Returns true if the string is not null |
| -z Str1 | Returns true if the string is null |
| Numeric Comparison | Description |
| expr1 -eq expr2 | Returns true if the expressions are equal |
| expr1 -ne expr2 | Returns true if the expressions are not equal |
| expr1 -gt expr2 | Returns true if expr1 is greater than expr2 |
| expr1 -ge expr2 | Returns true if expr1 is greater than or equal to expr2 |
| expr1 -lt expr2 | Returns true if expr1 is less than expr2 |
| expr1 -le expr2 | Returns true if expr1 is less than or equal to expr2 |
| ! expr1 | Negates the result of the expression |
| File Conditionals | Description |
| -d file | True if the file is a directory |
| -e file | True if the file exists (note that this is not particularly portable, thus -f is generally used) |
| -f file | True if the provided string is a file |
| -g file | True if the group id is set on a file |
| -r file | True if the file is readable |
| -s file | True if the file has a non-zero size |
| -u | True if the user id is set on a file |
| -w | True if the file is writable |
| -x | True if the file is an executable |