README.md

Batch launcher

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Th batch launcher or shebang is the first line of a script file that describe the interpreter to use (bash, ksh, awk, etc.).

Example:

#!/bin/bash

⚠️ The path to the used command must be absolute!
⚠️ The file must be in UNIX/Linux format with \n to mark end-of-line. Otherwise the used command /bin/bash\r with unexpected ending characters will not be found on the system and the script will not be executed.
⚠️ UTF BOM are forbidden in shell script because they insert caracters before the shebang!
0xEF 0xBB 0xBF!/bin/bash will not be executed because of 3 BOM characters (UTF-8 hexadecimal example).

Example of error obtained in the case of a Windows format script file:

-bash: ./windows-format-launcher.sh : /bin/bash^M : bad interpreter: No such file or directory

Using absolute path

The classic method:

#!/bin/bash

⚠️ only one option or group of options in a single block can be passed to the used command:

#!/bin/bash -i
#!/bin/bash -ix

Shebang examples:

#!/bin/bash
#!/usr/bin/bash
#!/usr/bin/ksh
#!/bin/sh
#!/bin/awk -f

Using env command

The intrepreter to use is passed as argument of the env command and will be search in directores defined on the PATH environement variable.

#!/usr/bin/env bash

⚠️ Options cannot be passed to the used interpreter on Linux. ⚠️ env command path must be absolute!

Shebang examples:

#!/bin/env bash
#!/usr/bin/env ksh93
#!/usr/bin/env sh

Known shebang

Some very usefull shebang:

Bourne shell (sh)

#!/bin/sh

Bourne again shell (bash)

#!/bin/bash

Korn shell (ksh)

#!/bin/ksh

AWK acript

#!/bin/awk -f

SED script

#!/bin/sed -f

nodejs script

#!/usr/bin/nodejs

⚠️ nodejs can be installed as node on some Linux distribution.