CronTab Common Errors and crontab Common Errors

CronTab Common Errors and crontab Common Errors

Environment Variable

When using environment variables, crontab may fail to normally access the environment variables in bashrc.

Therefore, you should be very careful when using crontab to access environment variables.

Between the third and fifth are "or" operations ("date" and "Week ")

Run a. sh at 07:30 on the first Sunday of June 17, May.

30 7 1-7 5 0 a. sh // incorrect usage, will be executed multiple times

30 7 1-7 5 * test'date + \ % w-eq 0 &&~ A. sh // extract the week of the current date and determine whether it is 0. a slash is used before %.

Use test to Judge 1 = 0, test1-eq 0, for example, test.

Minutes

Executed every two hours

 0*/2 * * * a.sh

How to Use test

 (EXPRESSION )

              EXPRESSIONis true

       !EXPRESSION

              EXPRESSIONis false

       EXPRESSION1-a EXPRESSION2

              bothEXPRESSION1 and EXPRESSION2 are true

       EXPRESSION1-o EXPRESSION2

              eitherEXPRESSION1 or EXPRESSION2 is true

       -nSTRING

              thelength of STRING is nonzero

       STRINGequivalent to -n STRING

       -zSTRING

              thelength of STRING is zero

       STRING1= STRING2

              thestrings are equal

       STRING1!= STRING2

              thestrings are not equal

       INTEGER1-eq INTEGER2

              INTEGER1is equal to INTEGER2

       INTEGER1-ge INTEGER2

              INTEGER1is greater than or equal to INTEGER2

       INTEGER1-gt INTEGER2

              INTEGER1is greater than INTEGER2

       INTEGER1-le INTEGER2

              INTEGER1is less than or equal to INTEGER2

       INTEGER1-lt INTEGER2

              INTEGER1is less than INTEGER2

       INTEGER1-ne INTEGER2

              INTEGER1is not equal to INTEGER2

       FILE1-ef FILE2

              FILE1and FILE2 have the same device and inode numbers

       FILE1-nt FILE2

              FILE1is newer (modification date) than FILE2

       FILE1-ot FILE2

              FILE1is older than FILE2

       -bFILE

              FILEexists and is block special

       -cFILE

              FILEexists and is character special

       -dFILE

              FILEexists and is a directory

       -eFILE

              FILEexists

       -fFILE

              FILEexists and is a regular file

       -gFILE

              FILEexists and is set-group-ID

       -GFILE

              FILEexists and is owned by the effective group ID

       -hFILE

              FILEexists and is a symbolic link (same as -L)

       -kFILE

              FILEexists and has its sticky bit set

       -LFILE

              FILEexists and is a symbolic link (same as -h)

       -OFILE

              FILEexists and is owned by the effective user ID

       -pFILE

              FILEexists and is a named pipe

       -rFILE

              FILEexists and read permission is granted

       -sFILE

              FILEexists and has a size greater than zero

       -SFILE

              FILEexists and is a socket

       -tFD  file descriptor FD is opened on a terminal

       -uFILE

              FILEexists and its set-user-ID bit is set

       -wFILE

              FILEexists and write permission is granted

       -xFILE

              FILEexists and execute (or search) permission is granted