Bash variables, quoting rules, parameter expansion, command substitution, arithmetic, globbing and exit codes.
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- How do you assign a value to a variable in Bash?
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var=value with no spaces around the equals sign- How do you access the value of a variable?
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Prefix the variable name with a dollar sign: $varname or ${varname}- What characters are allowed in Bash variable names?
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Alphanumeric characters and underscore; first character must be a letter or underscore- How do you remove a variable from the shell environment?
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Use the unset command: unset varname- What is an environment variable?
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A shell variable that is exported and inherited by child processes- How do you export a variable to make it available to child processes?
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Use the export command: export varname- What do single quotes prevent in Bash?
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All expansions and interpretations; everything inside single quotes is treated literally- Which special characters trigger expansion inside double quotes?
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Dollar sign ($) for variable and command substitution, and backtick for command substitution- What happens when you use a variable without quotes if it contains spaces?
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The variable value undergoes word splitting and pathname expansion (globbing)- What quoting style allows ANSI escape sequences like \n and \t?
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$'...' (ANSI-C quoting)- How do you include a literal single quote inside a single-quoted string?
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End the single-quoted string, add an escaped single quote \', then resume: 'can'\''t'- How do you prevent a dollar sign from triggering variable expansion?
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Escape it with a backslash: \$ inside double quotes- What is the result if you expand an unset variable inside double quotes?
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An empty string- Can backslash escape characters inside single quotes?
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No; backslash is literal inside single quotes- What is the advantage of using ${var} instead of $var?
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Braces are unambiguous when the variable name is followed by alphanumeric characters
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