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The test command

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The test command is a unix command. It is not a shell builtin command. It can test the existence and status of a variable, or to make comparisons on variables, files, ...
Test returns 0 if the condition is verified. We call the command, via test or [].

Comparing integers

• -eq

  equals

  if [ "$a" -eq "$b" ]

  will be true if the numbers contained in $a and $b variables are identical.

• -ne

  is not equal to

  if [ "$a" -ne "$b" ]

  will be true when the numbers contained in $a and $b variables are not identical.

• -gt

  is greater than

  if ["$a" -gt "$b" ]

  will be true when the number contained in $a variable is upper than the number contained in $b variable.

• -ge

  is greater than or equal to

  if [ "$a" -ge "$b" ]

  will be true when the number contained in $a variable is greater than or equal to $b.

• -lt

  is less than

  if [ "$a" -lt "$b" ]

  will be true when the number contained in $a variable is less than to $b.

• -le

  is less than or equal to

  if [ "$a" -le "$b" ]

  will be true when the number contained in $a variable is less than or equal to $b.

Comparing strings

• =

  equals

  if [ "$a" = "$b" ]

  will be true when $a and $b strings are identical.

• !=

  is not equal to

  if [ "$a" != "$b" ]

  will be true when $a and $b strings are not identical.

• <

  that is smaller, according to the alphabetical ASCII order

  if [[ "$a" < "$b" ]]

  if [ "$a" \< "$b" ]

  Note that < needs to be in an escape sequence if it is inside of [].

• >

  is greater than, according to the alphabetical ASCII order

  if [[ "$a" > "$b" ]]

  if [ "$a" > "$b" ]

  Note that > needs to be in an escape sequence if it is inside of [].

• -z

  The string is empty. That is to say that it has a zero size

  if [ -z "$a" ]

• -n

  The string is not empty.

  if [ -n "$a" ]

Testing files

• -e

  Check if file exists

  if [ -e "$fichier" ]

  will be true if the file exists.

• -r

  Check if the file is readable

  if [ -r "$fichier" ]

  will be true if the file exists and is readable.

• -w

  Checks if the file is writable

  if [ -w "$fichier" ]

  will be true if the file exists and is writable.

• -d

  Checks if the directory exists

  if [ -d "$repertoire" ]

  will be true if the directory exists.

   

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